AP Biology Set 2
In animal cells, cytokinesis occurs by a process known as
cleavage, forming a cleavage furrow
If the cell does not receive the go-ahead signal, it will
exit the cycle, switching into a nondividing state called the G0 phase
A ligand-gated ion channel receptor acts as a
gate when the receptor changes shape
Transcription alone does not constitute
gene expression
The mediator proteins interact with
general transcription factors at the promoter This helps assemble and position the preinitiation complex
In a literal sense, children do not inherit particular physical traits from their parents. It is ___ that are actually inherited.
genes
Mendel developed a hypothesis to explain the 3:1 inheritance pattern he observed in F2 offspring. Four related concepts make up this model. These concepts can be related to what we now know about
genes and chromosomes
Differential gene expression results from
genes being regulated differently in each cell type
A very small fraction of the non-protein-coding DNA consists of
genes for RNA such as rRNA and tRNA
The law of independent assortment applies only to
genes on different, nonhomologous chromosomes or those far apart on the same chromosome
In genomic imprinting,
genes whose expression is affected by the sex of the transmitting parent
An organism's traits do not always reveal its
genetic composition
If a mutation has an adverse effect on the phenotype of the organism, the condition is referred to as a
genetic disorder or hereditary disease
The two chromosomes in each pair are called
homologous chromosomes or homologs
An individual with the dominant phenotype could be either
homozygous dominant or heterozygous
Ovulation is the release of
egg from follicle Remaining follicle 🡪 corpus luteum (↑hormones)
Neurons use two types of signals to communicate:
electrical signals (long-distance) and chemical signals (short-distance)
Antigens are substances that can
elicit a response from a B or T cell
Mutations in the ras proto-oncogene and p53 tumor-suppressor gene are common in
human cancers
However, basic Mendelian genetics endures as the foundation of
human genetics
The synaptic terminal of one axon passes
information across the synapse in the form of chemical messengers called neurotransmitters
Biological clocks are typically synchronized to
light and dark cycles
Distances between genes can be expressed as
map units
Additional defenses unique to vertebrates are
natural killer cells, interferons (signaling proteins), and the inflammatory response
ncRNAs
non-protein-coding RNAs that play a role in gene expression
Ions are NOT able to diffuse freely through the membrane, because they are charged and so must
pass through protein channels specific for each ion.
Protein kinases transfer
phosphates from ATP to protein, a process called phosphorylation
Many relay molecules in signal transduction pathways are protein kinases, creating a
phosphorylation cascade
Polyploidy is common in
plants not animals
Enzymes in the eukaryotic nucleus modify
pre-mRNA (RNA processing) before the genetic messages are dispatched to the cytoplasm
Control elements and the transcription factors they bind are critical to the
precise regulation of gene expression in different cell types
Apoptosis
process of programmed cell death
After translation, polypeptides undergo
processing, including cleavage, and chemical modifications
Male reproductive system: role of LH?
produce testosterone
Cell differentiation is marked by the
production of tissue-specific proteins
Barrier defenses:
skin, mucous membranes, secretions
Antibodies do not kill pathogens; instead,
they mark pathogens for inactivation or destruction
conservative model
two parental strands reassociate after acting as templates for new strands thus restoring the parental double helix
In sexual reproduction
two parents give rise to offspring that have unique combinations of genes inherited from the two parents
The frequency of cell division varies with the
type of cell
Mutations of one or a few nucleotides can
affect protein structure and function
Every eukaryotic species has a characteristic number of
chromosomes in each cell nucleus
What is a homolog?
chromosomes that are similar in size, shape, and genes; Homologs are held together by the synaptonemal complex
Cycles of sleep and wakefulness are examples of
circadian rhythms, daily cycles of biological activity
The human brain contains about 100 billion neurons, organized into
circuits more complex than the most powerful supercomputers
Antigen-presenting cells have
class I and II MHC molecules on their surfaces
During the undershoot
membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close and resting potential is restored
The resting potential is the
membrane potential of a neuron not sending signals
Homologous pairs of chromosomes orient randomly at
metaphase l of meiosis
The strand used as the template is determined by
the orientation of the enzyme that transcribes the gene. This in turn, depends on the DNA sequences associated with the gene
Watson and Crick reasoned that
the pairing was more specific, dictated by the base structures
In DNA replication
the parent molecule unwinds, and two new daughter strands are built based on base-pairing rules
epitope
the part of an antigen molecule to which an antibody attaches itself
wild type
the phenotype for a character most commonly observed in natural populations
Termination of Transcription in Bacteria
the polymerase stops transcription at the end of the terminator and the mRNA can be translated without further modification
Which of the following is the best statement of the use of the addition rule of probability?
the probability that either one of two independent events will occur
Chromosomes in a homologous pair are
the same length and shape and carry genes controlling the same inherited characters
The net production (output) of one molecule of G3P requires ___ complete turns of the Calvin cycle, with one CO2 entering at each turn of the cycle
three
A trisomic zygote has
three copies of a particular chromosome
The neurons of the reticular formation control the
timing of sleep periods characterized by rapid eye movements (REMs) and by vivid dreams
Lymphocytes of the adaptive immune system do not travel to
tissues
Most WBC's are found within the
tissues of the body (ex. lymph nodes and spleen) not within the blood
Cells are organized successively into
tissues, organs, organ systems, and the whole organism
The spinal cord conveys information
to and from the brain
Most cells also exhibit anchorage dependence
to divide, they must be attached to a substratum
Pyrimidine + pyrimidine
too thin; DNA too thin
Purine + purine
too wide; DNA too thick
Cytotoxic T cells use
toxic proteins to kill cells infected by viruses or other intracellular pathogens
Each variant for a character, such as purple or white color for flowers, is called a
trait
In innate immunity, recognition and response rely on
traits common to groups of pathogens
mutant phenotypes
traits that are alternatives to the wild type
Eukaryotic cells modify RNA after
transcription
Malignant tumors invade surrounding tissues and can undergo
metastasis, the spread of cancer cells to other parts of the body, where they may form additional tumors
Hindbrain
metencephalon and myelencephalon
It seems that imprinting is the result of the
methylation (addition of —CH3 groups) of cysteine nucleotides
Biologists estimate that expression of at least one-half of human genes may be regulated by
miRNAs
p53 also activates expression of
miRNAs that inhibit the cell cycle, and can turn on genes directly involved in DNA repair
The mesencephalon develops into
midbrain
Meiosis II is very similar to
mitosis
During RNA processing a(n) _____ is added to the 5' end of the RNA.
modified guanine nucleotide
The cholera bacterium, Vibrio cholerae, produces a toxin that
modifies a G protein so that it is stuck in its active form
Some pathogens avoid destruction by
modifying their surface to prevent recognition or by resisting breakdown following phagocytosis
Class II MHC molecules provide the
molecular signature by which antigen-presenting cells are recognized
DNA methylation, the addition of methyl groups to certain bases in DNA, is associated with
reduced transcription in some species
promoter
region of DNA that indicates to an enzyme where to bind to make RNA The DNA sequence where RNA polymerase attaches
operator
region of chromosome in an operon to which the repressor binds when the operon is "turned off" Region of DNA that controls RNA polymerase's access to a set of genes with related functions.
The structural organization of chromatin helps
regulate gene expression
Ovulation
release of the ovum from the ovary (release of mature eggs) -Young produced when survival is most likely -Hormonal changes influenced by day length, season temp, rainfall or lunar cycles
The counter-regulatory functions of the pancreas refer to the fact that it
releases one hormone that reduces glucose levels in the blood and another that increases them
dephosphorylation
removal of a phosphate group from a molecule
An inversion is the
removal of a segment followed by its reinsertion into the same chromosome in the reverse orientation.
The antiparallel structure of the double helix affects
replication
G0
resting phase
rRNA
ribosomal RNA; type of RNA that makes up part of the ribosome
location of translation in eukaryotes
ribosome in the cytoplasm
A thick band of axons called the corpus callosum enables the
right and left cerebral cortices to communicate
long-distance signaling
signaling between cells separated by some distance (exocrine)
The role of DNA in heredity was first discovered by
studying bacteria and the viruses that infect them
To determine the genotype we can carry out a
testcross: breeding the mystery individual with a homozygous recessive individual
Gene expression orchestrates the
the developmental programs of animals
The basis for Chargaff's rules was not understood until
the discovery of the double helix
The first solid evidence associating a specific gene with a specific chromosome came in
the early 1900s from the work of Thomas Hunt Morgan
cri du chat
("cry of the cat") A child born with this syndrome is severely intellectually disabled and has a catlike cry; individuals usually die in infancy or early childhood
Oswald Avery, Maclyn McCarty, and Colin MacLeod (1944)
Detergent was used to lyse heat-killed S cells. The lysate from this was used for transformation assays. The heat-treated S lysate could change R to S- they concluded that the transforming principle was in the lysate. Each lysate component was tested to determine the transforming activity. First, the heat-killed S lysate was incubated with an enzyme (SIII)- this completely chewed up the sugar coat. The coat-less S lysates was also tested- it was able to transform; thus, the R strain was not just assembling a new S sugar coat from the pieces. Next, the coat-less S extract was incubated with trypsin and chymotrypsin (protein digesting enzymes)- this was able to transform, as well. Thus, the transforming activity was not protein. They precipitated nucleic acids (DNA and RNA) with alcohol- the nucleic acids were isolated from Pneumococcus. After dissolution in water, this solution was tested; RNA was destroyed using the RNase enzyme- the solution could transform so RNA was not the transforming principle. The remaining solution (pure DNA) was incubated with DNase (DNA-digesting enzyme). The solution was unable to transform. DNA is the transforming principle.
___ precedes differentiation
Determination
Alfred Hershey and Martha Chase
Determined that genetic DNA, not protein, was the genetic material using experiments about bacteriophages They designed an experiment showing that only one of the two components of T2 (DNA or protein) enters an E. coli cell during infection. They concluded that the injected DNA of the phage provides the genetic information.
List three reasons for cell division
Development (from a zygote) Growth Repair
What occurs in diabetes mellitus?
Diabetes mellitus is the result of a lack of insulin, or a decreased response to insulin in target cells. When blood glucose levels rise, the cells are unable to take up enough glucose to function properly. Thus, fat becomes the main source for cellular respiration. Acidic metabolites can form during fat breakdown and accumulate in the blood- this is dangerous because blood pH is lowered and sodium and potassium ions are depleted. "In people with diabetes mellitus, the level of glucose in blood may exceed the capacity of the kidneys to reabsorb this nutrient. Glucose that remains in the kidney filtrate is excreted. For this reason, the presence of sugar in urine is one test for this disorder. As glucose is concentrated in the urine, more water is excreted along with it, resulting in excessive volumes of urine. Diabetes (from the Greek diabainein, to pass through) refers to this copious urination; and mellitus (from the Greek meli, honey) refers to the presence of sugar in urine. (Diabetes insipidus, discussed in Chapter 44, is a rare disorder of kidney function that results in large volumes of dilute urine but no major disruption in glucose metabolism.)"
Erwin Chargaff
Discovered that DNA composition varies, but the amount of adenine is always the same as thymine and the amount of cytosine is always the same as guanine.
Frederick Griffith
Discovered transformation during an experiment that involved injecting mice with smooth S cells, rough R cells, heat-killed S cells, and heat-killed S cells with living R cells. Discovered transformation in pneumonia-causing bacteria.
Down Syndrome (Trisomy 21)
Down syndrome is an aneuploid condition that results from three copies of chromosome 21 It affects about one out of every 830 children born in the United States The frequency of Down syndrome increases with the age of the mother, a correlation that has not been explained
For his work, Morgan chose to study
Drosophila melanogaster, a common species of fruit fly
Testes
(inside scrotum) - produce sperm, sex hormones
The three stages of translation:
- Initiation - Elongation - Termination all three stages require protein "factors" that aid in the translation process. Energy is required for some steps, too
Elongation continues until
- a stop codon in the mRNA reaches the ribosome's A site - the completed polypeptide is freed - the ribosome splits back into its subunits
How are human mitochondria inherited?
- from the mother only - An individual's mitochondria are all derived from those found in the ovum.
Termination of Translation
- occurs when the codon in A-site is a stop codon - release factor places a water molecule on the polypeptide chain and thus releases the protein
How does "the Pill" work?
-"the Pill" is an oral contraceptive -Contains estrogen and progesterone -First available in 1960 Main effect: Prevent ovulation Other effects: -Thickens cervical mucus - slows down sperm -Thins uterus lining - prevent implantation of fertilized egg Usage: active pill for 21 days, inactive pills for 7 days ("period") Other medical uses: -Medication for mild/moderate acne -Decrease painful menstruation -Treat polycystic ovary syndrome (PCOS)
The membrane potential of a neuron in rest (not sending a signal). It is typically between
-60 and -80 millivolts (mV).
Many animals have a complex nervous system that consists of
-A central nervous system (CNS), where integration takes place; this includes the brain and a nerve cord -A peripheral nervous system (PNS), which carries information into and out of the CNS
For a recessive X-linked trait to be expressed,
-A female needs two copies of the allele (homozygous) -A male needs only one copy of the allele (hemizygous)
Duchenne muscular dystrophy
-Affects 1/3500 males born in the US -Characterized by a progressive weakening of the muscles and loss of coordination -Sufferers rarely live past early 20s -Results due to an absence of a muscle protein called dystrophin; located on a specific locus on the X chromosome
Crossing Over and Synapsis During Prophase I
-After interphase the sister chromatids are held together by proteins called cohesins -The nonsister chromatids are broken at precisely corresponding positions -A zipper-like structure called the synaptonemal complex holds the homologs together tightly -DNA breaks are repaired, joining DNA from one nonsister chromatid to the corresponding segment of another
There are two additional types of phagocytic cells:
-Dendritic cells stimulate development of adaptive immunity -Eosinophils discharge destructive enzymes against parasites
Amniotic embryos
-Develop in fluid-filled sac w/in a shell or uterus -Amnion: fluid protects embryo - prevent dehydration, cushions mechanical shock -Yolk : nutrients in egg -Mammalian eggs: little stored food
The same hormone may have different effects on target cells that have
-Different receptors for the hormone -Different signal transduction pathways
Each tRNA molecule enables translation of a given mRNA codon into a certain amino acid.
-Each carries a specific amino acid on one end -Each has an anticodon on the other end; the anticodon base-pairs with a complementary codon on mRNA
Types of asexual reproduction
-Fission: parent separates into 2+ individuals of same size -Budding: outgrowths from parent (eg. cnidarians, tunicates) -Fragmentation: breaking of body into pieces, form into adults by regeneration (eg. sea stars, sponges, cnidarians) -Parthenogenesis: female produces eggs that develop w/o fertilization (eg. male bees - haploid)
There are three main types of membrane receptors:
-G protein-coupled receptors -Receptor tyrosine kinases -Ion channel receptors
Interphase (about 90% of the cell cycle) can be divided into three phases:
-G1 phase ("first gap") -S phase ("synthesis") -G2 phase ("second gap")
The brain and spinal cord contain
-Gray matter, which consists of neuron cell bodies, dendrites, and unmyelinated axons -White matter, which consists of bundles of myelinated axons
X Inactivation in Female Mammals
-In mammalian females, one of the two X chromosomes in each cell is randomly inactivated during embryonic development -The inactive X condenses into a Barr body -If a female is heterozygous for a particular gene located on the X chromosome, she will be a mosaic for that character
Proto-oncogenes can be converted to oncogenes by
-Movement of DNA within the genome: if it ends up near an active promoter, transcription may increase -Amplification of a proto-oncogene: increases the number of copies of the gene -Point mutations in the proto-oncogene or its control elements: cause an increase in gene expression
There are two main types of phagocytic cells, which engulf and destroy pathogens, in the mammalian body:
-Neutrophils circulate in the blood -Macrophages migrate through the body or reside permanently in organs and tissues
Tumor-suppressor proteins
-Repair damaged DNA -Control cell adhesion -Act in cell-signaling pathways that inhibit the cell cycle in the cell-signaling pathway
Other advantages of Mendel using peas
-Short generation time -Large numbers of offspring -Mating could be controlled; plants could be allowed to self-pollinate or could be cross-pollinated
Point mutations within a gene can be divided into two general categories:
-Single nucleotide-pair substitutions -Nucleotide-pair insertions or deletions
Three events are unique to meiosis, and all three occur in meiosis I. They are:
-Synapsis and crossing over in prophase I: Homologous chromosomes physically connect and exchange genetic information -Homologous pairs at the metaphase plate -Separation of homologs during anaphase I
Each end of a pre-mRNA molecule is modified in a particular way
-The 5′ end receives a modified nucleotide 5′ cap -The 3′ end gets a poly-A tail
In vertebrates
-The CNS is composed of the brain and spinal cord -The PNS is composed of nerves and ganglia Region specialization is a hallmark of both systems
A ribosome has three binding sites for tRNA. They are:
-The P site holds the tRNA that carries the growing polypeptide chain -The A site holds the tRNA that carries the next amino acid to be added to the chain -The E site is the exit site, where discharged tRNAs leave the ribosome
Communication between animal cells through secreted signals can be classified by two criteria:
-The type of secreting cell -The route taken by the signal in reaching its target
Cancer cells do not need growth factors to grow and divide:
-They may make their own growth factor -They may convey a growth factor's signal without the presence of the growth factor -They may have an abnormal cell cycle control system
The 5' cap and poly-A tail share several functions. They are:
-They seem to facilitate the export of mRNA to the cytoplasm -They protect mRNA from hydrolytic enzymes -They help ribosomes attach to the 5′ end
The difference between tyrosine kinase and protein kinase
-Tyrosine kinase is a membrane enzyme receptor. When activated by a signal molecule it is phosphorylated. It does not phosphorylate something else. Once phosphorylated it can activate a variety of specific relay proteins to illicit a cellular response. -Protein kinases are enzymes within the cell. They are not part of the membrane. Protein kinases are involved in signal transduction pathways.
Inheritance of characters by a single gene may deviate from simple Mendelian patterns in the following situations:
-When alleles are not completely dominant or recessive -When a gene has more than two alleles -When a gene produces multiple phenotypes
The idea of the gene has evolved through the history of genetics. We have considered a gene as
-a discrete unit of inheritance -a region of specific nucleotide sequence in a chromosome -a DNA sequence that codes for a specific polypeptide chain
translocation (translation)
-completes the cycle -ribosome advances three nucleotides along the mRNA in the 5' to 3' direction -concurrently, the uncharged tRNA from the P site is expelled and the peptidly-tRNA from the A site moves into the P site -ribosome has an empty A site ready for the entry of the aminoacyl-tRNA corresponding to the next codon
Breakage of a chromosome can lead to four types of changes in chromosome structure:
-deletion -duplication -inversion -translocation
Multicellular eukaryotes depend on cell division for
-development from a fertilized egg -growth -repair
In metaphase I,
-pairs of homologs line up at the metaphase plate, with one chromosome facing each pole -Microtubules from one pole are attached to the kinetochore of one chromosome of each pair -Microtubules from the other pole are attached to the kinetochore of the other chromosome
Elongation of the Polypeptide Chain
During elongation, amino acids are added one by one to the C-terminus of the growing chain Each addition involves proteins called elongation factors and occurs in three steps: codon recognition, peptide bond formation, and translocation Energy expenditure occurs in the first and third steps
If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the genotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?
0 homozygous black (BB): 1 heterozygote (black) (Bb): 1 homozygous orange (bb) The heterozygous black-eyed MendAlien has the genotype Bb. The orange-eyed MendAlien has the genotype bb. The result of this cross is two Bb offspring and two bb offspring. This 2:2 ratio reduces to 1:1.
In a situation in which genes assort independently, what is the ratio of the gametes produced by an AaBB individual?
1 AB : 1 aB
Black eyes are dominant to orange eyes, and green skin is dominant to white skin. Sam, a MendAlien with black eyes and green skin, has a parent with orange eyes and white skin. Carole is a MendAlien with orange eyes and white skin. If Sam and Carole were to mate, the predicted phenotypic ratio of their offspring would be _____.
1 black eyes, green skin : 1 black eyes, white skin : 1 orange eyes, green skin : 1 orange eyes, white skin Sam's genotype is BbGg, and Carole's genotype is bbgg.
An individual heterozygous for eye color, skin color, and number of eyes mates with an individual who is homozygous recessive for all three characters; what would be the expected phenotypic ratio of their offspring? [Hint: B = black eyes, b = orange eyes; G = green skin, g = white skin; C = two eyes, c = one eye]
1 black eyes, green skin, two eyes : 1 black eyes, green skin, one eye : 1 black eyes, white skin, two eyes : 1 black eyes, white skin, one eye : 1 orange eyes, green skin, two eyes : 1 orange eyes, green skin, one eye : 1 orange eyes, white skin, two eyes : 1 orange eyes, white skin, one eye This is a tough problem; you had to expand your Punnett square to accommodate another character. However, 1:1:1:1:1:1:1:1 ratio is the expected outcome of a BbGgCc x bbggcc cross.
XXX females occur with a frequency of about
1 in 1,000 They are healthy, with no unusual physical features, though they are at risk for learning disabilities
Sickle-cell disease affects
1 in 400 African Americans
One map unit represents a
1% recombination frequency
The nitrogenous base is attached to the sugar's
1' carbon and the phosphate group is attached to the sugar's 5' carbon.
Which strand of DNA is the template strand?
During transcription, the gene determines the sequence of nucleotide bases along the length of the RNA molecule (that is being made). Only one of the two DNA strands is transcribed. This strand is known as the template strand because it acts as a template in the synthesis of RNA. "For any given gene, the same strand is used as the template every time the gene is transcribed. For other genes on the same DNA molecule, however, the opposite strand may be the one that always functions as the template."
In spatial summation
EPSPs produced nearly simultaneously by different synapses on the same postsynaptic neuron add together
Anaphase
Each chromatid is pulled toward the pole to which it is attached by spindle fibers.
Segregation in a heterozygous plant is like flipping a coin:
Each gamete has a ½ chance of carrying the dominant allele and a ½ chance of carrying the recessive allele
Four Phases of Menstrual Cycle:
1) Follicular Phase : low estrogen, ↑FSH = egg develops in ovary 2) Ovulation (Day 14): ↑LH = egg released into Fallopian tube 3) Luteal Phase : -↑progesterone, ↑estrogen = lining of uterus thickens to prepare for pregnancy -Egg travels down Fallopian tube, waits for fertilization 4) Menstruation (no fertilization) : -↓P/↓E = lining of uterus breaks down -Blood and unfertilized egg discharged
Formation of Zygote
1) Ovulation 2) Fertilization occurs 3) Cleavage starts 4) Cleavage continues 5) The blastocyt implants
Mammalian Fertilization
1) Sperm binds to receptors in zona pellucida (extreacellular matrix of egg) 1-2. Acrosomal reaction: sperm releases hydrolytic enzymes to digest zona pellucida (depolarization of membrane to prevent other sperm from brinding) 3. Sperm + egg fuse 4. Cortical reaction: sperm+ egg fusion triggers release of Ca²⁺ (cortical ganules fule with z.p., causing z.p. to harden and form fetilization envelope 5. Ca²⁺ release also triggers activation of the egg
Explain how the light signal causes the greening response.
1) The phytochrome receptor detects the light signal. It activates at least two signal transduction pathways 2) One pathway activates an enzyme which produces cGMP- it uses cGMP as a second messenger (This activates a protein kinase). The other pathway increases the cytosolic level of Ca2+ and opens Ca2+ channels (this activates another, different protein kinase) 3) The two pathways lead to expression of genes for proteins that act in the de-etiolation response. 4) Thus, de-etiolation (the greening response) occurs.
List of basic steps that occur in transduction
1) The receptor (protein) receives a signal -This can be a G protein coupled receptor or a tyrosine-kinase receptor 2) A conformational change occurs 3) An intracellular relay pathway (signal transduction) is triggered 4) Often a second messenger is activated that initiates and coordinates the transduction 5) A cellular response occurs
The law of independent assortment states that
Each pair of alleles segregates independently of each other pair of alleles during gamete formation
The Three Stages of Labor
1) dilation of the cervix 2) expulsion: delivery of the infant 3) delivery of the placenta
Why are there often so many steps between the original signal event and the cell's response?
Each step in a cascade produces a large number of activated products, causing signal amplification as the cascade progresses. This amplification permits the signaling molecule to have a widespread effect throughout the cell.
Female reproductive system: role of FSH?
Egg development (in follicle)
Oogenesis
Egg production -Ova production -Before birth: oogonia 🡪 meiosis - STOP at Prophase I (primary oocytes) -Puberty: each month, egg in follicle 🡪 Meiosis I (secondary oocytes) 🡪 fertilization 🡪 Meiosis II -1 ovum + 3 polar bodies
Explain the difference between an endocrine gland and an exocrine gland. Give an example of each.
Endocrine cells get grouped in ductless organs- these are known as endocrine glands. Endocrine glands secrete hormones directly into the fluid surrounding it. Exocrine glands, on the other hand, have ducts that transport secreted substances onto body surfaces or into body cavities. An example of an endocrine gland is the thyroid gland of the neck while an example of an exocrine gland is the mammary glands.
A simple endocrine pathway:
Endocrine cells respond to a change in some internal or external variable—the stimulus—by secreting hormone molecules that trigger a specific response by target cells. A simple neuroendocrine pathway: Sensory neurons respond to a stimulus by sending nerve impulses to a neurosecretory cell, triggering secretion of a neurohormone. Upon reaching its target cells via the bloodstream, the neurohormone binds to its receptor, triggering signal transduction that results in a specific response."
In addition to genes what else can have an effect on phenotype? Provide an example.
Environmental influences can have an effect on phenotype. Traits that depend on multiple genes combined with environmental influences are multifactorial. Hydrangeas grown in basic soil appear pink. Hydrangea of the same genetic variety grown in acidic soil with free aluminum appear blue.
List three important facts about the promoter.
1) promoter of a gene includes within it the transcription start point 2) promoter typically extends several dozen of more nucleotide pairs upstream from the start point 3) RNA Polymerase binds in a precise location and orientation on the promoter
The human X chromosome contains about
1,100 genes
Initiation of Transcription
1. A eukaryotic promoter 2. Several transcription factors bind to DNA. 3. Transcription initiation complex forms.
What three things does sensation require?
1. A stimulus (which is detected by a sensory receptor) 2. An action potential (the sensory receptor translating the stimulus into a nervous signal) 3. The signal is then interpreted by the brain
Mendel's model
1. Alternative versions of genes account for variations in inherited characters. 2. For each character an organism inherits two copies of a gene, one from each parent. 3. If two alleles at the locus differ, then the dominant allele determines the organism's appearance, the recessive has no noticeable effect. 4. Law of segregation
Binary fission steps
1. Chromosome replication begins. 2. One copy of the origin is now at each end of the cell. 3. Replication finishes 4. Two daughter cells result.
List the three stages of translation and very briefly explain each.
1. Initiation "The start codon (AUG) signals the start of translation. First, a small ribosomal subunit binds with mRNA and a special initiator tRNA. Then the small subunit moves along the mRNA until it reaches the start codon. Proteins called initiation factors bring in the large subunit that completes the translation initiation complex. 2. Elongation "During elongation, amino acids are added one by one to the C-terminus of the growing chain. Each addition involves proteins called elongation factors. Elongation occurs in three steps: codon recognition, peptide bond formation, and translocation. Energy expenditure occurs in the first and third steps." "Translation proceeds along the mRNA in a 5′ → 3′ direction. The ribosome and mRNA move relative to each other, codon by codon. The elongation cycles takes less than a tenth of a second in bacteria." 3. Termination "Elongation continues until a stop codon in the mRNA reaches the A site of the ribosome. The A site accepts a protein called a release factor. The release factor causes the addition of a water molecule instead of an amino acid. This reaction releases the polypeptide, and the translation assembly comes apart."
inflammatory response
1. Mast cells release histamines. Capillaries dilate. 2. Neutrophils and anti-microbial peptides enter tissue. 3. Neutrophils digest pathogens and cell debris. Tissue heals.
At resting potential
1. Most voltage-gated sodium (Na+) and potassium (K+) channels are closed
Division in meiosis I occurs in four phases:
1. Prophase I 2. Metaphase I 3. Anaphase I 4. Telophase I and cytokinesis
Division in meiosis II also occurs in four phases:
1. Prophase II 2. Metaphase II 3. Anaphase II 4. Telophase II and cytokinesis
Process of phagocytosis (immune response)
1. Pseudopodia surround pathogens. 2. Pathogens are engulfed by endocytosis. 3. Vacuole forms. 4. Vacuole and lysosome fuse. 5. Pathogens destroyed. 6. Debris from pathogens released.
Termination (translation)
1. Ribosome reaches a stop codon on mRNA 2. Release factor promotes hydrolysis 3. Ribosomal subunits and other components dissociate
miRNA binding to mRNA steps
1. The miRNA binds to a target mRNA 2. If bases are complementary, mRNA is degraded; if the match is less complete, translation is blocked
Normal cell cycle-inhibiting pathway
1. UV light leads to DNA damage in genome 2. Protein kinases 3. Active form of p53 4. Transcription 5. Protein that inhibits the cell cycle 6. Damaged DNA is not replicated (no cell division)
Accurate translation requires two steps
1. a correct match between a tRNA and an amino acid, done by the enzyme aminoacyl-tRNA synthetase 2. a correct match between the tRNA anticodon and an mRNA codon
Steps of the Calvin Cycle
1. carboxylation 2. reduction 3. regeneration 4. carbohydrate synthesis
Initiation of Translation
1. small subunit of ribosome attaches to 5' end of mRNA (ribosome binding site) 2. initiator aminoacyl tRNA (attached to f-Met) binds to start codon (AUG) 3. large subunit of ribosome binds (initiator tRNA occupies P site)
Translation process
1. the exposed codon in the first site attract complementary tRNA bearing an amino acid. The tRNA pairs with the mRNA codon, bringing it very close to the other tRNA molecule 2. the ribosome forms a bond between the two amino acids and breaks the bond between the first tRNA and its amino acid 3. the ribosome pulls the mRNA strand the length of one codon. The first tRNA is shifted into the exit site, where it leaves the ribosome and returns to the cytoplasm to recharge. The first site is again empty by exposing the next mRNA codon.
Two organisms with genotype AaBbCcDdEE mate. These loci are all independent. What fraction of the offspring will have the same genotype as the parents?
1/16 Breaking the question down into individual loci makes it simpler. The offspring of Aa ×Aa will be Aa 50% (one-half) of the time. The same is true for Bb, Cc, and Dd. Two EE individuals can only have EE offspring, so that probability is 1. The chance of an offspring being identical to the parent is therefore (1/2)4, or 1/16.
Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of crosses BbTt × BBtt will be expected to have black fur and long tails?
1/2
In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?
1/64
How many neurons in the brain
100 billion
The human brain has 100 billion neurons, which make
100 trillion connections
How many sperm is released per ejaculation?
100-650 million
___ of all human cancers involve viruses
15-20%
All cells of mammalian embryos are totipotent until the
16 cell stage
At the end of meiosis I there are
2 haploid cells
Multiple step signaling pathways provide signal amplification. How might this be beneficial?
Enzyme cascades work to amplify the cell's response to a signal Thus, at each step the number of activated products can be much greater than in the step before When the signal is amplified, so is the response If some of the molecules in the pathway relay the signal to numerous molecules in the next step, a larger number of activated molecules is the end result
RNA polymerase
Enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription Enzyme that links together the growing chain of ribonucleotides during transcription.
Protein phosphatases
Enzymes that can rapidly remove phosphate groups from proteins, a process called dephosphorylation
Process of DNA replication
Enzymes unzip the DNA by breaking the hydrogen bonds between base pairs The enzyme DNA polymerase joins individual nucleotides to form the complimentary strand to the existing DNA single strand DNA polymerase also proof reads each new DNA strand to make sure each new molecule is an exact copy of the original DNA molecule
explain the signal transduction pathway for epinephrine
Epinephrine binds to a G protein-coupled receptor in the plasma membrane of target cells, in the liver. This binding triggers a cascade of events including production of cAMP as a second messenger. cAMP activates protein kinase A, which activates an enzyme required for glycogen breakdown and inactivates an enzyme necessary for glycogen synthesis. Thus, liver releases glucose into the bloodstream.
When an action potential is generated,
2. Voltage-gated Na+ channels open first and Na+ flows into the cell 3. During the rising phase, the threshold is crossed, and the membrane potential increases 4. During the falling phase, voltage-gated Na+ channels become inactivated; voltage-gated K+ channels open, and K+ flows out of the cell
How many amino acids are there?
20
There are ___ amino acids, but there are only ___ nucleotide bases in DNA
20; four
Each set of 23 consists of
22 autosomes and a single sex chromosome
For humans, the haploid number is
23 (n=23)
Human somatic cells have
23 pairs of chromosomes
Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?
25 The offspring would be in a 3:1 ratio of normally pigmented mice to albino mice.
The number of combinations possible when chromosomes assort independently into gametes is
2^n, where n is the haploid number
If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be
2x
___ mRNA is more long-lived than ___ mRNA
Eukaryotic; prokaryotic
How many nucleotides are required to code for amino acids?
3 "Triplets of nucleotide bases are the smallest units of uniform length that can code for all the amino acids. If each arrangement of three consecutive nucleotide bases specifies an amino acid, there can be 64 (that is, 4^3) possible code words—more than enough to specify all the amino acids. Experiments have verified that the flow of information from gene to protein is based on a triplet code: The genetic instructions for a polypeptide chain are written in the DNA as a series of nonoverlapping, three-nucleotide words. The series of words in a gene is transcribed into a complementary series of nonoverlapping, three-nucleotide words in mRNA, which is then translated into a chain of amino acid."
In the second part of Phase 3, 3 ___ molecules are used to convert the _ ___ into _ ___ (Calvin cycle)
3 ATP molecules are used to convert the 3 R5P into 3 RuBP.
To produce 1 molecule of G3P (which contains 3 carbons), the Calvin cycle must take up
3 molecules of CO2 (1 carbon atom each).
In the first part of Phase 3 (Calvin cycle), 5 molecules of G3P (1 phosphate group each) are converted to
3 molecules of R5P (also 1 phosphate group each). Thus there is a net release of 2 Pi.
The remaining 5 G3P molecules (15 total carbon atoms) enter Phase 3, where they are converted to
3 molecules of R5P.
At the end of Phase 2 of the Calvin cycle, 1 of the 6 G3P molecules is output from the cycle, removing
3 of the 18 carbons.
Nucleotides are added to the ___ end of the growing RNA molecule
3'
New nucleotides are added to the
3' end
Given the parents AABBCc × AabbCc, assume simple dominance for each trait and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?
3/4
Mendel's model accounts for the
3:1 ratio observed in the F2 generation of Mendel's crosses
At the end of meiosis II there are typically
4 haploid cells
Meiosis results in
4 haploid daughter cells one set of chromosomes in each gamete
Human gestation (pregnancy) =
40 weeks
For humans, the diploid number is
46 (2n=46)
How many codons are there
4^3 = 64. 300 codons in an mRNA -> 100 polypeptides in the amino acid
An Okazaki fragment has which of the following arrangements?
5' RNA nucleotides, DNA nucleotides 3'
tRNA is roughly L-shaped with the
5' and 3' ends both located near one end of the structure
A new DNA strand can elongate only in the
5' to 3' direction
The direction of synthesis of an RNA transcript is _____.
5' —> 3' Nucleotides are added to the 3' end of RNA
How many nucleotides are in a primer?
5-10
A ___ frequency of recombination is observed for any two genes on different chromosomes
50%
Genes that are far apart on the same chromosome can have a recombination frequency near
50%
When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?
50%
Whereas genes located on different chromosomes assort independently and have a recombination frequency of ___, linked genes have a recombination frequency that is ___ ___ ___ .
50%; less than 50%
What chance does a cell have of receiving either the maternal or paternal chromosome?
50/50
The rate of elongation is about
500 nucleotides per second in bacteria and 50 per second in human cells
During translation, the mRNA base triplets, called codons, are read in the
5′ → 3′ direction
Translation proceeds along the mRNA in a
5′ → 3′ direction
The 3 CO2 molecules are added to 3 RuBP molecules (which contain 15 total carbon atoms), next producing
6 molecules of 3-PGA (18 total carbon atoms).
In Phase 2 (Calvin cycle), six of the ATP and all of the NADPH are used in Phase 2 to convert
6 molecules of PGA to 6 molecules of G3P. Six phosphate groups are also released in Phase 2 (derived from the 6 ATP used).
How many codons actually code for amino acids?
61 3 triplets are "stop" signals to end translation
The fusion of two gametes (each with 8.4 million possible chromosome combinations from independent assortment) produces a zygote with any of about
70 trillion diploid combinations
For humans (n = 23), there are more than ___ possible combinations of chromosomes
8 million (2^23)
Note that in the entire Calvin cycle,
9 ATP are hydrolyzed to ADP; 8 of the 9 phosphate groups are released as Pi, and the ninth phosphate appears in the G3P output from the cycle.
Interphase is about ________ of the cell cycle
90%
More than ___ of the human protein-coding genes undergo alternative splicing
90%
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?
92 Mitosis follows the duplication of the cell's DNA.
caspase
A "killer enzyme" that plays a role in apoptosis, or programmed cell death
chromosome theory of inheritance
A basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.
antigen-presenting cell
A cell that displays foreign antigens with major histocompatibility complexes on their surfaces
relay proteins
A cellular protein that transfers a signal from a receptor molecule to another part of the cell
Aneuploidy
A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number.
Tetraploidy
A chromosomal number that is four times the haploid number, having four copies of all autosomes and four sex chromosomes (4n)
initiation factors
A class of proteins that assist ribosomes in binding to a messenger RNA molecule to begin translation.
Hermaphroditism
A condition in which an individual has both female and male gonads and functions as both a male and female in sexual reproduction by producing both sperm and eggs. -Sessile/burrowing animals - barnacles, parasites (tapeworms), earthworms
In codominance
A condition in which neither of two alleles of a gene is dominant or recessive. two dominant alleles affect the phenotype in separate, distinguishable ways
What is the difference between a haploid and a diploid cell?
A diploid cell, created through mitosis, has two sets of chromosomes (2n), one from the mother and one from the father. For humans, the diploid number is 46. A haploid (2n) cell contains a single set of chromosomes (one from the mother or one from the father). Gametes are haploid; for humans, the haploid number is 23.
limbic system
A doughnut-shaped system of neural structures at the border of the brainstem and cerebral hemispheres; associated with emotions such as fear and aggression and drives such as those for food and sex. Includes the hippocampus, amygdala, and hypothalamus.
What is the TATA box? How do you think it got this name?
A eukaryotic promoter includes a TATA box, a nucleotide sequence containing TATA, about 25 nucleotides upstream from the transcriptional start point. A TATA box is a promoter crucial in forming the initiation complex in eukaryotes. The promoter got its name due to the nucleotide bases it contains.
Innate immunity
A form of defense common to all animals that is active immediately upon exposure to pathogens and that is the same whether or not the pathogen has been encountered previously. Immunity that is present before exposure and effective from birth. Responds to a broad range of pathogens.
ras gene
A gene that codes for Ras, a G protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases, ultimately resulting in stimulation of the cell cycle.
regulatory gene
A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.
proteasomes
A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin. giant protein complexes that bind protein molecules and degrade them
complement system
A group of about 30 blood proteins that may amplify the inflammatory response, enhance phagocytosis, or directly lyse extracellular pathogens.
prostaglandins
A group of bioactive, hormone-like chemicals derived from fatty acids that have a wide variety of biological effects including roles in inflammation, platelet aggregation, vascular smooth muscle dilation and constriction, cell growth, protection of from acid in the stomach, and many more.
Helper T cell
A helper T cell activates both the humoral and cell-mediated immune responses. For this to be possible, a foreign molecule must be present that binds specifically to the antigen receptor of the T cell. Secondly, the antigen must be displayed on the surface of an antigen-presenting cell, which can be a dendritic cell, macrophage or B cell.
How many chromosomes are in a human cell?
A human cell has 46 chromosomes or 2 sets of 23 chromosomes (one maternal and one paternal)
Huntington's disease
A human genetic disease caused by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms.
DNA ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.
Fragmentation
A means of asexual reproduction whereby a single parent breaks into parts that regenerate into whole new individuals.
map units
A measurement of the distance between genes; one map unit is equivalent to a 1 percent recombination frequency.
5′ cap
A modified form of guanine nucleotide added onto the 5′ end of a pre-mRNA molecule.
ligand
A molecule that binds specifically to another molecule, usually a larger one.
Briefly describe two genetic disorders caused by *aneuploidy*.
A monosomic zygote has one copy of a specific chromosome while a trisomic zygote has three copies of a specific chromosome.
Acetylcholine
A neurotransmitter that enables learning and memory and also triggers muscle contraction
In prophase II
A new spidle apparatus forms around the chromosomes.
introns
A noncoding, intervening sequence within a eukaryotic gene.
If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred?
A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell. When this error occurs in meiosis II, only half of the gametes are affected.
Have you ever seen a shriveled potato sending out skinny, pale sprouts? What is this called?
A potato left to grow in darkness will send out pale, skinny, short roots. These are adaptations for when the potato is in darkness. The process is called etiolation.
TATA box
A promoter DNA sequence crucial in forming the transcription initiation complex.
What is the function of a protein kinase?
A protein kinase is an enzyme that activates/inactivates other proteins by phosphorylation (adding a phosphate group) them. Some protein kinases give the go-ahead signals at the G1 and G2 checkpoints.
Single-strand binding proteins
A protein that binds to the unpaired DNA strands during DNA replication, stabilizing them and holding them apart while they serve as templates for the synthesis of complementary strands of DNA. bind to and stabilize single-stranded DNA
Topoisomerase
A protein that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork. relieves the strain of twisting of the double helix by breaking, swiveling, and rejoining DNA strands
repressor
A protein that suppresses the transcription of a gene.
Aster
A radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis.
nucleotide excision repair
A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.
phosphorylation cascade
A series of enzyme-catalyzed phosphorylation reactions commonly used in signal transduction pathways to amplify and convey a signal inward from the plasma membrane.
signal transduction pathway
A series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response.
G protein-coupled receptors
A special class of membrane receptors with an associated GTP binding protein; activation of a G protein-coupled receptor involves dissociation and GTP hydrolysis
Inducer
A specific small molecule that inactivates the repressor in an operon.
centrosome
A structure in animal cells containing centrioles from which the spindle fibers develop.
mitogen
A substance that induces or stimulates mitosis
What is the purpose of a test cross?
A test cross is carried out to determine whether an individual with a dominant phenotype is either homozygous dominant or heterozygous.
semen
A thick fluid containing sperm and other secretions from the male reproductive system alkaline fluid w/nutrients, enzymes
Zona pellucida
A thick, transpartent coating rich in glycoproteins that surrounds an egg.
codons
A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.
mRNA
A type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.
In alternative RNA splicing,
A type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.
alternative RNA splicing
A type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns. Consequently, the number of different proteins an organism can produce is much greater than its number of genes
In epistasis
A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited. one gene affects the phenotype of another due to interaction of their gene products
bacteriophages
A virus that infects bacteria; also called a phage.
Which of these is a testcross?
A? x aa A testcross is used to determine whether an individual expressing the dominant phenotype is homozygous dominant or heterozygous.
What are the products of linear electron flow?
ATP and NADPH
Which codon is the START codon (i.e. establishes the reading frame)?
AUG
start codon
AUG (methionine)
Advantage of asexual reproduction
Ability to reproduce quickly if environment is stable
Which microfilaments and motor proteins proteins are associated with cleavage?
Actin, myosin and ATP The contractile ring tightens around the cytoplasm until the cell is pinched inward
Why is it not good to have excessive numbers of HER2 receptors?
Excessive numbers of HER2 receptors mean an excessive amount of HER2 can bind in a cell. Patients with breast cancer cells that have excessive levels of HER2 have a poor prognosis. Researchers, though, have developed a protein called Herceptin that binds to Her2 on the cells and inhibits its growth- this stops further tumor development
Postsynaptic potentials fall into two categories
Excitatory postsynaptic potentials (EPSPs) Inhibitory postsynaptic potentials (IPSPs)
There are many different types of neurotransmitters. Each neuron secretes only one type of neurotransmitter. Some neurotransmitters hyperpolarize the postsynaptic membrane. Are these excitatory or inhibitory neurotransmitters?
Excitatory postsynaptic potentials (EPSPs) are depolarizations- they bring the membrane potential towards threshold. Inhibitory postsynaptic potentials (IPSPs) are hyperpolarizations- they move the membrane potential farther away from threshold. Neurotransmitters that hyperpolarize the postsynaptic membrane are inhibitory neurotransmitters.
The RNA segments joined to one another by spliceosomes are _____.
Exons
Activation of B cells
Activation of B cells involves helper T cells and proteins on the surface of pathogens. When an antigen binds a B cell, the cell takes in a few foreign molecules by receptor-mediated endocytosis. The class II MHC protein of the B cell then presents an antigen fragment to a helper T cell, a process that is critical to B cell activation. An activated B cell gives rise to thousands of identical plasma cells. These begin producing and secreting antibodies. Most antigens recognized by B cells contain multiple epitopes. A variety of B cells activated by one antigen will give rise to plasma cells producing antibodies directed against different epitopes of the common antigen. Antibodies do not kill pathogens; instead, they mark pathogens for inactivation or destruction In neutralization, antibodies bind to viral surface proteins, preventing infection of a host cell. Antibodies may also bind to toxins in body fluids and prevent them from entering body cells. B cells can express five different forms (or classes) of immunoglobulin (Ig) with similar antigen-binding specificity but different heavy chain C regions IgD is membrane bound, while the other four, IgA, IgE, IgG, and IgM, are soluble
What is the difference between heterozygous and homozygous individuals?
All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.
The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?
All of the genes controlling the traits behaved as if they were on different chromosomes.
genome
All the genetic information in an organism; all of an organism's chromosomes.
A proposed explanation for the surprisingly low number of genes in the human genome
Alternative RNA splicing Alternative RNA splicing can significantly expand the repertoire of a eukaryotic genome
There are four aspects of signal regulation. They are:
Amplification of the signal (and thus the response) Specificity of the response Overall efficiency of response, enhanced by scaffolding proteins Termination of the signal
transfer RNA (tRNA)
An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA
Why is a RNA primer required before DNA can be synthesized and which enzyme synthesizes this primer?
An RNA primer is required before DNA can be synthesized because DNA polymerase is unable to start producing a DNA chain from scratch. Primase synthesizes RNA primers.
How does a myelin sheath speed impulse transmission?
An action potential's speed increases as the axon's diameter increases. Myelin sheath work as insulators- thus, they increase the speed of action potentials. Nodes of Ranvier, gaps in the myelin sheath, house voltage-gated sodium channels. Thus, the action potentials in myelinated axons jump between the nodes of Ranvier- this is saltatory conduction.
What is an afferent neuron? Efferent?
An afferent neuron is a sensory neuron that carries impulses from stimuli to the CNS. Efferent neurons are motor neurons that carry impulses away from the CNS and towards the muscles.
primer
An already existing RNA chain bound to template DNA to which DNA nucleotides are added during DNA synthesis.
telomerase
An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells.
nuclease
An enzyme that cuts DNA or RNA, either removing one or a few bases or hydrolyzing the DNA or RNA completely into its component nucleotides.
primase
An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.
aminoacyl-tRNA synthetase
An enzyme that joins each amino acid to the appropriate tRNA.
Helicases
An enzyme that untwists the double helix of DNA at the replication forks, separating the two strands and making them available as template strands.
List the three components of a tyrosine-kinase receptor
An extracellular ligand-binding site An α helix spanning the membrane An intracellular tail containing multiple tyrosines
List the components of an operon and explain the role of each. *Note that the regulatory gene is not part of the operon.
An operon consists of the operator, the promoter, and the genes that they control. Operators act as the on-off switch in the operon; binding of protein repressors and reduce or even stop transcription, and when neither of these molecules are present, transcription goes on. The promoter is the RNA polymerase binding site and it is where the genes are transcribed from. The genes in an operon function in the same process and are, thus, found together "The repressor prevents gene transcription by binding to the operator and blocking RNA polymerase. The repressor is the product of a separate regulatory gene, located some distance from the operon itself."
genetic map
An ordered list of the genetic loci along a particular chromosome.
homozygous
An organism that has two identical alleles for a trait
clone
An organism that is genetically identical to the organism from which it was produced
genotype
An organism's genetic makeup, or allele combinations.
phenotype
An organism's physical appearance, or visible traits.
Somatic cells
Any cells in the body other than reproductive cells
Variation
Any difference between individuals of the same species.
How does random fertilization contribute to genetic variation?
Any sperm can fuse with any ovum. The fusion of the two games (each one with 8.4 million possible chromosome combinations due to independent assortment) produces a zygote with any of 70 trillion diploid combinations.
Elongation of the RNA Strand
As RNA polymerase moves along the DNA, it untwists the double helix, 10 to 20 bases at a time. Transcription progresses at a rate of 40 nucleotides per second in eukaryotes. A gene can be transcribed simultaneously by several RNA polymerases. Nucleotides are added to the 3′ end of the growing RNA molecule.
Budding
Asexual reproduction in which a part of the parent organism pinches off and forms a new organism
parthenogenesis
Asexual reproduction in which females produce offspring from unfertilized eggs.
Contrast the way T cell receptors recognize and bind with antigens with the way that B cell receptors do?
B cell antigen receptors bind to the epitopes of intact antigens circulating in bodily fluids. T cell antigen receptors, on the other hand, only bind to fragments of antigens that are presented on the surface of host cells. The host protein that presents the antigen fragment on the surface of the cell is called an MHC (major histocompatibility complex) molecule.
Clonal selection is the division of _____ that have been stimulated by binding to an antigen, which results in the production of cloned _____.
B cells ... plasma cells and memory cells The antigen-selected proliferation of B cells produces clones of plasma cells and memory cells.
How does quorum sensing work?
Bacterial cells secrete small molecules that are detected by other bacterial cells. These molecules act as signaling molecules- the concentration of these signaling molecules is sensed by a bacteria. It allows the bacteria to monitor the local density of the cell population. This sensing allows bacterial populations to regulate their behaviors so as to undergo activities that need to be performed when a certain number of cells are in synchrony.
Recall that target cells have receptors for specific hormones. Where are the receptors for lipid- soluble hormones found?
Based on chemical structures and solubility in lipids, hormones are divided into two groups. Lipid-soluble hormones include steroid and thyroid hormones while water-soluble hormones include amines, peptides and proteins. Lipid-soluble hormones, as a result of their solubility in lipids, easily diffuse through the plasma membrane. They pass through the membrane and bind with an intracellular receptor located in the cytoplasm or nucleus, which then forms a hormone-receptor complex. This complex influences gene activation and production of proteins.
Purines
Bases with a double-ring structure. Adenine and guanine.
Pyrimidines
Bases with a single-ring structure. Adenine and thymine.
What is happening to the molecules (in feedback inhibition) to cause them to behave differently?
Because the end product allosterically inhibits enzymatic activity, the substrate cannot bind to the active site of the enzyme and, thus, the metabolic pathway does not occur. The molecules behave differently due to the feedback control done by the end product.
Why are the strands synthesized differently?
Because the strands of DNA are antiparallel, they must be synthesized differently. Both strands are synthesized in the 5' to 3' direction but the leading strand is synthesized continuously while the lagging strand is synthesized discontinuously with Okazaki fragments.
How does the result differ from that of cell division in a multicellular eukaryote?
Binary fission is seen in prokaryotes (simple cells that do not have a nucleus). This form of cell division does not include spindle formation or sister chromatids which translates to a faster process than mitosis. In binary fission, the cells divide in order to reproduce while in mitosis, the cells divide in order to grow, or to replace old/damaged cells.
Lipid-soluble: mode of travel in bloodstream
Bind to transport proteins, keeping them soluble in the bloodstream
How are the concentration gradients of Na+ and K+ maintained?
Both Na+ and K+ have concentration gradients across the membrane of a neuron. These gradients are maintained by sodium-potassium pumps in the membrane. The pumps use energy from ATP hydrolysis to transport Na out of the cell and K into the cell (active transport; 3 NA for 2 K).
hybridization
Breeding technique that involves crossing dissimilar individuals to bring together the best traits of both organisms
What is the function of Catabolite activator protein (CAP)
CAP acts as a glucose sensor; it activates transcription of the operon (and aids RNA polymerase in transcription) when glucose levels are low. CAP senses glucose indirectly through cAMP (which is present in high levels when glucose is low). "The CAP binding site is a positive regulatory site that is bound by catabolite activator protein (CAP). When CAP is bound to this site, it promotes transcription by helping RNA polymerase bind to the promoter...As it turns out, RNA polymerase alone does not bind very well to the lac operon promoter. It might make a few transcripts, but it won't do much more unless it gets extra help from catabolite activator protein (CAP). CAP binds to a region of DNA just before the lac operon promoter and helps RNA polymerase attaches to the promoter, driving high levels of transcription."
What is carbon fixation?
Carbon fixation is the start of the Calvin cycle. It is a process in which CO2 (carbon dioxide) is incorporated into organic molecules. This process is catalyzed by rubisco.
transduction (signal transduction)
Cascades of molecular interactions relay signals from receptors to target molecules in the cell
The chief caspase in the nematode is called
Ced-3
response (signal transduction pathway)
Cell signaling leads to regulation of transcription or cytoplasmic activities
Cell to cell recognition is a type of local signaling. How does it differ from other types of local signaling?
Cell to cell recognition is different from other types of local signaling because it doesn't involve a transfer of molecules between cells. With cell to cell recognition, two cells bind to one another. This is the signal for either one, or both, of the cells to begin transduction.
How do cells most often communicate with each other?
Cells mainly communicate with each other through the use of chemical signals. There are various types of chemical signal communication, including autocrine, paracrine, direct and endocrine (hormone). With chemical signaling, only certain cells can be acted upon. Only certain cells have the structure to bind to certain chemicals released- so though the chemical released may travel throughout the body, it only affects certain cells. The difference between the different forms of chemical signalling is how far the signal has to travel to reach its destination cell.
Mast cells
Cells that release chemicals (such as histamine) that promote inflammation.
Certain cancers, including chronic myelogenous leukemia (CML), are caused by
Certain cancers, including chronic myelogenous leukemia (CML), are caused by
Quantitative characters
Characters that vary in the population along a continuum (in gradations).
Prophase
Chromosomes are tightly coiled Mitotic spindle begins to form Centrosomes move away from each other Nuclear envelope fragments
In early prophase I,
Chromosomes condense, spindle apparatus forms, nuclear envelope begins to break down. Synapsis (pairing) of homologous chromosomes.
chromatin
Clusters of DNA, RNA, and proteins in the nucleus of a cell
Some disorders caused by recessive alleles on the X chromosome in humans:
Color blindness (mostly X-linked) Duchenne muscular dystrophy Hemophilia
What is the difference between complete and incomplete dominance?
Complete dominance occurs when the phenotypes of the heterozygote and dominant homozygote are identical. In incomplete dominance, the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties (red and white flowers create pink flowers).
Human embryonic development
Conception: in oviduct Implantation: in uterus Hormones: -Human Chorionic Gonadotropin (hCG): maintain estrogens in early pregnancy; pregnancy test
Alfred Sturtevant
Constructed a gene map of the fruit fly using crossing over frequencies.
Recombination between linked genes comes about for what reason?
Crossovers between these genes result in chromosomal exchange.
Menstrual cycle
Cycle during which an egg develops and is released from an ovary and the uterus is prepared to receive a fertilized egg.
What is the function of cAMP?
Cyclic AMP (cAMP) is a "hunger signal" produced by E.coli when the glucose levels of the cell are low. cAMP binds to CAP and changes its shape to make it able to bind DNA and promote transcription (that produces enzymes that break down lactose). Without cAMP, CAP cannot bind DNA and is, thus, inactive. "High glucose → Low cAMP. Low glucose → High cAMP."
What is the final step in the cell-mediated response to a viral infection?
Cytotoxic T lymphocytes punch holes in the membranes of infected host cells. This step causes infected host cells to disintegrate and prevents the virus from spreading to other cells.
___ is the genetic material
DNA
The radioactive isotope 32P labels the T2 phage's _____.
DNA The T2 phage consists of a protein coat and DNA. It is the DNA that contains P.
Hereditary information is encoded in
DNA encoded in DNA and reproduced in all cells of the body
A virus is
DNA (sometimes RNA) enclosed by a protective coat, often simply protein
The central dogma of molecular biology is
DNA -> RNA -> Protein
When T. H. Morgan's group showed that genes are located on chromosomes, what components of chromosomes became candidates for genetic material?
DNA and protein
In 1950, Erwin Chargaff reported that
DNA composition varies from one species to the next This evidence of diversity made DNA a more credible candidate for the genetic material
Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?
DNA in both daughter cells would be radioactive.
In preparation for cell division
DNA is replicated and the chromosomes condense
In 1952, Alfred Hershey and Martha Chase showed that
DNA is the genetic material of a phage known as T2
What is the function of DNA ligase?
DNA ligase seals the gaps between DNA fragments.
Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?
DNA polymerase III
Which enzyme(s) catalyze the synthesis of new DNA at the replication fork?
DNA polymerases catalyze the synthesis of new DNA at a replication fork.
Which enzymes proofread DNA as it is being synthesized?
DNA polymerases proofread newly made DNA and replace any incorrect nucleotides as it is being synthesized.
S (synthesis)
DNA replication
Many proteins work together in
DNA replication and repair
DNA replication is the process by which DNA makes a copy of itself during cell division. Where does DNA replication begin and how does it differ in prokaryotes and eukaryotes?
DNA replication begins at sites called origins of replication, where the two DNA strands are separated, opening up a replication bubble. A eukaryotic chromosome may have hundreds or thousands of origins of replication while a prokaryote has only one. Replication proceeds in both directions from each origin, until the entire molecule is copied
Meselson and Stahl cultured E. coli for several generations in a medium with a heavy isotope of nitrogen, 15N. They transferred the bacteria to a medium with a light isotope of nitrogen, 14 N. After two rounds of DNA replication, half the DNA molecules were light (both strands had 14N) and half were hybrids (15N-14N). What did the researchers conclude from these results?
DNA replication is semiconservative.
The genetic code is redundant but not ambiguous
DNA sequence may have repeats in codons and therefore in anticodons and amino acids, but each codon codes for a specific amino acid and is not open to interpretation about which amino acid. Many codons code for different amino acids , but each codon has its own amino acid. more than one codon may specify a particular amino acid but no codon specifies more than one amino acid
Template in Transcription
DNA strand
The two strands of DNA are antiparallel to one another (their subunits run in opposite directions). Explain why the strands run antiparallel.
DNA strands are antiparallel and complementary. The strands run in opposite directions (one strand starts at the 5' and ends at 3'; the other starts at the 3' and ends at 5'). It is the orientation of the deoxyribose molecules that are opposite to each other.
DNA replication
DNA unzips into two parts and splits with the cell. In it's new home each side of the DNA strand attack to matching nucleotides to create 2 exact copies. It is important in puberty and other times of growth as it is the reproducing of your cells.
Franklin's X-ray crystallographic images of DNA enabled Watson to deduce that
DNA was helical
Transcription is the
DNA-directed synthesis of RNA
Which of the following mutations would likely be most dangerous to a cell?
Deletion of one nucleotide would shift the reading frame, altering the coding for all subsequent amino acids. In most cases, this would destroy the function of the protein produced from this gene.
Where are dendritic cells commonly located?
Dendritic cells are commonly located in tissues that are exposed to the external environment, like the skin or the inner linings of the nose. They can also be located in the inner linings of the lungs, stomach and intestines.
List AND briefly explain two external physical factors that affect cell division.
Density-dependent inhibition -Cells form a single layer; this means that crowded cells will stop dividing -If some cells are removed, those that border the open space will begin dividing again and stop once the space is filled Growth factors -Proteins that signal the cell when to move through the cell cycle and divide -Stimulate other cells to divide
Frederick Griffith (1928)
Experimented with mice and strains of Pneumococcus- S strains are smooth (each bacterium has a sugar capsule which protects the S bacteria from the host's immune system; the strain is infectious) and R colonies are rough (bacterium do not have capsule coats so they are not infectious). The mice that Griffith injected with the S strain contracted pneumonia and died within a few days. The mice injected with the R strain did not contract pneumonia. Based on these findings, Griffith experimented further- he heated-killed the S strain culture- when the mice were injected with this, no infection was seen. He also inected the heat-killed S with live R into the mice- they contracted pneumonia and died. He was able to isolate the live S strain from the mice blood. The S strain culture from the infected mice was capable of infecting other mice- the change was inherited by future descendants. Griffith concluded that something was transferred from the heat-treated S to the R strain. Thus, the R transformed into the infective S strain with a smooth coat. He called the phenomenon transformation ("a change in genotype and phenotype due to the assimilation of external DNA by a cell").
The hybrid offspring of the P generation are called the
F1 generation
When F1 individuals self-pollinate or cross-pollinate with other F1 hybrids, the
F2 generation is produced
Mendel developed a hypothesis to explain the 3:1 inheritance pattern he observed in
F2 offspring
When Mendel crossed the F1 hybrids, many of the
F2 plants had purple flowers, but some had white
Imagine a human disorder that is inherited as a dominant, X-linked trait. How would the frequency of this disorder vary between males and females?
Females would display this disorder with greater frequency than males. Men have only one X chromosome, whereas women have two. Remember that the disorder is caused by a dominant allele, so an individual who inherits a single dominant allele will display the disorder. Men have only one X chromosome, whereas women have two. Thus, women have twice the chance of inheriting the dominant allele that causes this disorder. Remember that the disorder is caused by a dominant allele, so an individual who inherits a single dominant allele will display the disorder. Read about the inheritance of X-linked genes.
The chromatin/chromosome concept is confusing.
First you see chromatin, then you see duplicated chromatin (the DNA has been replicated in the S phase of interphase), then you see condensed duplicated chromatin = chromosome. Now...If the chromosome was cut in half longitudinally there would be two sister chromatids. When the sister chromatids are pulled apart during cell nuclear division each of the chromatids can either be called chromatids or chromosomes.
Steps of Engelmann's experiment
First, Engelmann used a prism to disperse white light from the sun into the colors (wavelengths) of the visible spectrum. Then, using a microscope, he illuminated a filament of green algae with the visible spectrum. The photosynthetic pigments in the alga absorbed some of the wavelengths of light, using the absorbed energy to drive the reactions of photosynthesis, including oxygen production. Engelmann used his recently discovered aerotactic bacteria to determine which wavelengths of light caused the alga to photosynthesize most. Because the aerotactic bacteria were attracted to areas of highest oxygen concentration, they congregated around the regions of the alga that photosynthesized the most. He then counted the bacteria associated with each region of the alga illuminated by the various colors of light.
Ribosome Association and Initiation of Translation
First, a small ribosomal subunit binds with mRNA and a special initiator tRNA Then the small subunit moves along the mRNA until it reaches the start codon (AUG) Proteins called initiation factors bring in the large subunit that completes the translation initiation complex
wobble
Flexibility in the base-pairing rules in which the nucleotide at the 5' end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position of a codon. A violation of the base-pairing rules in that the third nucleotide (5' end) of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon.
Scientists expected to find one aminoacyl-tRNA synthetase per codon, but far fewer have been discovered. How does wobble explain this?
Flexible pairing at the third base of a codon is known as wobble. This allows some tRNAs to bind to more than one codon. "A wobble base pair is a pairing between two nucleotides in RNA molecules that does not follow Watson-Crick base pair rules. The four main wobble base pairs are guanine-uracil, hypoxanthine-uracil, hypoxanthine-adenine, and hypoxanthine-cytosine."
Example of a corepressor
For example, E. coli can synthesize the amino acid tryptophan when it has insufficient tryptophan By default, the trp operon is on and the genes for tryptophan synthesis are transcribed When tryptophan is present, it binds to the trp repressor protein, which turns the operon off The repressor is active only in the presence of its corepressor tryptophan; thus the trp operon is turned off (repressed) if tryptophan levels are high
Example of epistasis
For example, in Labrador retrievers and many other mammals, coat color depends on two genes. One gene determines the pigment color (with alleles B for black and b for brown). The other gene (with alleles E for color and e for no color) determines whether the pigment will be deposited in the hair. If heterozygous black labs (genotype BbEe) are mated, we might expect the dihybrid F2 ratio of 9:3:3:1. However, a Punnett square shows that the phenotypic ratio will be 9 black to 3 chocolate to 4 yellow labs. Epistatic interactions produce a variety of ratios, all of which are modified versions of 9:3:3:1.
alternative versions of genes account for variations in inherited characters
For example, the gene for flower color in pea plants exists in two versions, one for purple flowers and the other for white flowers These alternative versions of a gene are called alleles. Each gene resides at a specific locus on a specific chromosome.
Describe Thomas Morgan's experiment
For his work, Morgan chose to study Drosophila melanogaster, a common species of fruit fly. Morgan noted wild type, or normal, phenotypes that were common in the fly populations Traits alternative to the wild type are called mutant phenotypes. The first mutant Morgan discovered was a fly with white eyes instead of the wild-type red eyes.
How do point mutations differ from frameshift mutations?
Frameshift mutations can be caused by either insertions or deletions of base pair (s) in DNA and they alter the reading frame from the location of the mutation to the end of the gene; furthermore, an insertion of a stop codon where it doesn't belong may be present in a frame mutation. When point mutations occur, the reading frame of the gene remains the same because only a single nucleotide pair is altered.
De-etiolation activates enzymes that
Function in photosynthesis directly Supply the chemical precursors for chlorophyll production Affect the levels of plant hormones that regulate growth
Other components of cAMP pathways are
G proteins, G protein-coupled receptors, and protein kinases
For many cells, the ___ checkpoint seems to be the most important
G1
After mitosis and cytokinesis, the newly formed daughter cells enter the
G1 phase
Three important checkpoints are those in the
G1, G2, and M phases
The Calvin cycle requires a total of 9 ATP and 6 NADPH molecules pe
G3P output from the cycle (per 3 CO2 fixed).
What is bound to G protein that keeps it in the inactive state?
GDP (GTP without a phosphate group, thus it is inactive) keeps the G protein inactive. When GDP is bound to the G protein, the G protein is inactive.
nodes of Ranvier
Gaps in the myelin sheath to which voltage-gated sodium channels are confined.
memory cells
General term for lymphocytes that are responsible for immunological memory and protective immunity.
Humans are not good subjects for genetic research
Generation time is too long Parents produce relatively few offspring Breeding experiments are unacceptable
linked genes
Genes located on the same chromosome that tend to be inherited together in genetic crosses.
What are linked genes and how do affect independent assortment?
Genes that are located near each other on the same chromosome are called linked genes. They tend to be inherited together in genetic crosses. When geneticists follow linked genes in breeding experiments, the results deviate from those expected from Mendel's law of independent assortment. Morgan experimented with fruit flies to see how linkage would affect inheritance of two characters- he crossed flies that were different in body color and wing size. The first cross was a P generation cross that generated F1 dihybrid flies. The second cross was a testcross. Morgan discovered that body color and wing size are usually inherited together in specific combinations, parental phenotypes. These genes didn't assort independently- his reasoning was that they were on the same chromosome. Nonparental phenotypes were also produced in the testcross.
homeotic genes
Genes that determine basic features of where a body part is.
Ovaries
Glands that produce the egg cells and sex hormones
Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?
Golgi-derived vesicles
G2 (second gap)
Grows more as it prepares for cell division
A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
HT
Erwin Chargaff (1947)
He isolated DNA from different organisms and measured the levels of each of the nitrogenous bases. He found that the amount of adenine is close to the amount of thymine. He also found that the amount of guanine is close to the amount of cytosine. A = T; G = C.
Some human cells divide once every 24 hours. Where in the body might you find cells that divide infrequently?
Heart cells, brain cells, liver cells
B cell activation
Helper T cell binds to MHC complex Secretes cytokines that promote B cell activation and division
_____ interact with the antigen-class II MHC complex presented by macrophages.
Helper T cells Specific helper T cells recognize specific antigen-class II MHC complexes. The result of this is an activated helper T cell that stimulates both humoral and cell-mediated immune responses.
Describe the role of histamine in the inflammatory response.
Histamine is stored in the granules of mast cells, which are found in connective tissue. Histamine triggers blood vessels to dilate and become more permeable. When the vessels dilate, Neutrophils and antimicrobial peptides (short chains of amino acids that circulate throughout the body of an organism, inactivating or killing fungi and bacteria by disrupting their plasma membranes) enter tissue. Neutrophils then digest pathogens and cell debris (pus can be seen). The tissue heals.
In anaphase I
Homologous chrmosomes move to the oppisite poles of the cell. -pairs of homologous chromosomes separate -One chromosome of each pair moves toward opposite poles, guided by the spindle apparatus -Sister chromatids remain attached at the centromere and move as one unit toward the pole
How does independent assortment contribute to variation?
Homologous pairs of chromosomes orient randomly at metaphase I. In independent assortment, each pair of chromosomes sort maternal and paternal homologs into daughter cells independently of the other pairs. "The number of combinations possible when chromosomes assort independently into gametes is 2n, where n is the haploid number." Thus, for humans, there are more than 8 million possible combinations of chromosomes. There are an immense amount of combinations and, consequently, the possible chromosome combinations are varied.
Provide an example of a lethal dominant allele.
Huntington's disease
Nucleotides are added to a growing DNA strand as nucleoside triphosphates. What is the significance of this fact?
Hydrolysis of the two phosphate groups (P-Pi) and DNA polymerization are a coupled exergonic reaction.
How can a base-pair substitution result in a silent mutation?
If a base pair is substituted for another base pair that produces the same amino acid, a silent mutation occurs. For example, AAA may be altered to AAG but both codons code for the same amino acid (lysine). Consequently, the amino acid sequence stays the same because of redundancy in the genetic code.
Bacteria that are *conservative* with respect to gene expression are favored by natural selection. Why aren't all genes on at the same time?
If all genes were on at the same time, and were producing substances the cell was not in need of, precious sources, like energy, would be wasted to help produce these substances. Thus, the cell regulates the production of enzymes and other substances by feedback inhibition or gene regulation.`
What is aneuploidy?
If either of the affected gametes unites with a normal one during fertilization, the zygote will also have an abnormal number of a specific chromosome: this is aneuploidy. "Aneuploidy may involve more than one chromosome."
Gregor Mendel set up a dihybrid cross with one pea plant from the parental generation (P) producing round yellow peas and the other pea plant producing wrinkled green peas. The F2 generation included 315 plants producing round yellow peas, 108 with round green peas, 101 with wrinkled yellow peas, and 32 with wrinkled green peas. How would these results have differed if pea shape and pea color had been linked genes, located close together on the same chromosome?
If pea shape and pea color were determined by closely linked genes, they would not show independent assortment. Chromosomes would carry the combination of alleles seen in the P generation: yellow + round or green + wrinkled. Approximately ¾ or 75% of the F2 generation would inherit at least one chromosome carrying the yellow + round alleles. That is higher than Mendel's observed percentage of 315/556 or 56%.
What is the cause of nondisjunction?
If the members of a pair of homologous chromosomes do not separate properly during meiosis I or sister chromatids do not separate during meiosis II, nondisjunction occurs. As a result, one gamete receives two of the same type of chromosome, and another gamete receives no copy.
A single postsynaptic neuron can be affected by neurotransmitter molecules released by many other neurons, some releasing excitatory and some releasing inhibitory neurotransmitters. What will determine whether an action potential is generated in the postsynaptic neuron?
If the postsynaptic potentials released are large enough to invoke an action potential, it will occur- an action potential will be generated in the postsynaptic neuron.
If you move the potato into the light, the sprout will respond by forming short, sturdy stems and broad, green leaves. What is this response to light called?
If the potato is moved into the light, the potato will form short, sturdy stems and broad, green leaves. This is called de-etiolation.
B cells can express five different forms (or classes) of immunoglobulin (Ig) with similar antigen-binding specificity but different heavy chain C regions. They are?
IgD is membrane bound, while the other four, IgA, IgE, IgG, and IgM, are soluble
Passive immunity provides immediate, short-term protection. It is conferred naturally when
IgG crosses the placenta from mother to fetus or when IgA passes from mother to infant in breast milk
Hemocytes
Immune cells that circulate within the hemolymph of insects and ingest foreign substances by phagocytosis; secrete antimicrobial peptides
primary immune response
Immune response the first time the body is exposed to a particular antigen. Does not peak until 10-17 days after exposure. A clone of lymphocytes is formed
In one sentence state how animal and plant cell cytokinesis processes differ.
In animal cells, cytokinesis occurs by cleavage (a ring of actin filaments is formed at the metaphase plate)- the cells form a cleavage furrow (the ring contracts) which then pinches them into two; in plant cells, a cell plate is formed during cytokinesis- the two cells divide.
Gastrulation:
In animal development, a series of cell and tissue movements in which the blastula-stage embryo folds inward, producing a three-layered embryo, the gastrula.
What is the definition of an operon?
In bacteria, genes that are functionally related may be found in a cluster on the chromosome. This entire stretch of DNA is known as an operon. The operon can be controlled by an on-off switch (the switch is a segment of DNA called an operator, usually positioned within the promoter).
What is the name of the sequence that signals the end of transcription (in bacteria)?
In bacteria, the terminator sequence in the DNA signals the end of transcription. The transcribed terminator (which is now RNA) acts as a termination signal and causes the polymerase to detach from the DNA and release the transcript which will then be translated.
What are the two main ways of controlling metabolism in bacterial cells?
In bacterial cells, the two main ways of controlling metabolism are by feedback inhibition or by gene regulation. One mechanism for gene expression control in bacteria is the operon model.
What is a Barr body?
In mammalian females, one of the inherited X chromosomes is randomly inactivated during embryonic development. The inactive X condenses into a Barr body. Most of the genes of the X chromosome that form the Barr body are not expressed. In the varies, Barr-body chromosomes are reactivated in the cells that produce eggs so that every female gamete has an active X. If a female is heterozygous for a particular gene located on the X chromosome, she will be a mosaic
How is apoptosis involved in human development?
In mammals (including humans), several pathways (including 15 caspases) can carry out apoptosis. This process can be triggered by signals from outside or inside the cell. Internal signals can result from irreversible DNA damage or excessive protein misfolding. Apoptosis is a key part in the development of hands and feet in human beings. The interdigital tissue undergo apoptosis and as a result there is space between fingers and toes.
Differences in translation between prokaryotes and eukaryotes
In prokaryotes, translation of mRNA can begin before transcription has finished (due to a lack of compartmentalization) In a eukaryotic cell, the nuclear envelope separates transcription from translation
Which of the following provides an example of epistasis?
In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.
How do the offspring of sexually reproducing organisms differ from asexually reproducing organisms?
In sexual reproduction, two parents give birth to offspring that have unique combinations of genes that were inherited by both parents. In asexual reproduction, a single individual passes all of its genes to its offspring without the fertilization of gametes. The offspring of sexually reproducing organisms have varying genes from their parents; they aren't genetically identical with their parents. The offspring of asexually reproducing organisms are clones, and are thus genetically identical to their parent.
Distinguish between type 1 diabetes and type 2 diabetes.
In type 1 diabetes, insulin (which takes glucose out of the bloodstream) is not released so blood sugar levels remain high. This is treated by injection of exogenous insulin, which has the same effect as normal insulin. In type 2 diabetes, insulin is released as blood glucose rises but the cells don't receive or respond to the signal. One treatment is Avania, which increases cell sensitivity to glucose.
Is incomplete dominance considered blending inheritance? Why or why not?
Incomplete dominance is not considered blending inheritance (which would mean that the red/white trait would never show up again in the subsequent generations of the pink hybrids). Alleles can be segregated but the heritable factors maintain their identity in the hybrids; their inheritance is particulate.
In independent assortment
Independent segregation of genes during the formation of gametes each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs
Compare and contrast interferons and complement
Interferons are proteins that provide innate immunity by interfering in viral infections. Body cells that have been infected with viruses secrete interferons, which then cause proximal uninfected cells produce substances that inhibit viral reproduction. Essentially, interferons inhibit the cell-to-cell spread of viruses in the body. The complement system is comprised of about 30 proteins in the blood plasma. These proteins circulate in an inactive state and are activated by substances located on the surface of many microbes. Upon activation, a cascade of biochemical reactions occur which may lead to lysis of invading cells.
The mitotic phase alternates with
Interphase of the cell cycle
Which of the following most accurately describes a cyclin?
It activates a Cdk molecule when it is in sufficient concentration.
What happens to RNA polymerase II after it has completed transcription of a gene?
It is free to bind to another promoter and begin transcription. The enzyme is free to transcribe other genes in the cell.
Which of the following is true about a plant with the genotype AABbcc?
It is homozygous at two loci.
Is it possible for two organisms to have the same phenotype but a different genotype? Why or why not?
It is possible for two organisms to have the same phenotype (for example, purple flowers) but different genotypes. This is because the purple flower trait is dominant- a dominant trait always masks a recessive trait even in heterozygous "relationships." Consequently, an organism can have a genotype of Pp, with a phenotype of purple flowers because P (purple) is the dominant trait) while an organism with a genotype of PP will have the same phenotype (purple).
Sodium-potassium pumps use the energy of ATP to maintain
K+ and Na+ gradients across the plasma membrane
When gated (not leak) K+ channels open,
K+ diffuses out, making the inside of the cell more negative
Explain how sexual reproduction evolved
Least Complex to Most Complex Least Complex -No gonads -Egg/sperm develop in undifferentiated cells -Released into coelom, shed into environment Most complex -Distinct gonads (organs that produce gametes) -Delivery systems
Which are more common - lethal dominant alleles or lethal recessive alleles?
Lethal recessive alleles are more common than dominant alleles. All lethal alleles come about due to mutations in cells that produce gametes. A lethal recessive allele can be passed from one generation to the next by heterozygous carriers because the carriers have regular phenotypes. A lethal dominant allele usually results in the death of affected individuals before they can reproduce so the allele isn't passed on to subsequent generations.
Paracrine signaling: signaling molecule
Local regulators
Synaptic signaling: signaling molecule
Local regulators (neurotransmitters) that are carrying a chemical signal
LH
Luteinizing hormone, ovulation and egg release, maturation of egg, release of testosterone in males.
Which of the following triggers the cell's passage past the G2 checkpoint into mitosis?
MPF
Describe the process of phagocytosis by macrophages.
Macrophages carry out phagocytosis (ingestion and digestion of foreign substances including bacteria) to eliminate nonspecific threats to the human individual. Firstly, pseudopodia surround the pathogens. The pathogens are then engulfed (taken into the cell) by endocytosis. A vacuole forms around the pathogens. This pathogen-containing vacuole fuses with a lysosome (a vacuole containing digestive enzymes). The pathogens are then destroyed. The debris from the pathogens are released out of the macrophage.
Why are males more likely to exhibit X-linked recessive disorders?
Males are more likely to exhibit X-linked recessive disorders because they need only one copy of the allele in order for it to be expressed. They are hemizygous.
Do the levels of protein kinases vary?
Many of the kinases (that drive the cell cycle) are present at a constant concentration in a growing cell; most of the time, they are spent in an inactive form. To become active, a kinase must be attached to a cyclin (a protein that is called that because its concentration is clyclically fluctuating in the cell).
How many polypeptide chains interact to make the hemoglobin protein?
Many proteins are made from two or more different polypeptide chains (each polypeptide is specified by its gene). Hemoglobin, a protein that helps red blood cells transport oxygen, is made of two kinds of polypeptide chains interacting (and 4 polypeptide chains)- two genes code for the protein.
Cytoplasmic determinants
Maternal substances in egg that influence the course of early development. chemical signals such as mRNAs and transcription factors, influence pattern of cleavage
MPF
Maturation-promoting factor (M-phase-promoting factor); a protein complex required for a cell to progress from late interphase to mitosis. The active form consists of cyclin and a protein kinase.
For each character, an organism inherits two alleles, one from each parent
Mendel made this deduction without knowing about chromosomes. The two alleles at a particular locus may be identical, as in the true-breeding plants of Mendel's P generation. Or the two alleles at a locus may differ, as in the F1 hybrids
State Mendel's first law and explain it.
Mendel's first law is known as the law of segregation. "Thus, an egg or a sperm gets only one of the two alleles that are present in the organism. This segregation of alleles corresponds to the distribution of homologous chromosomes to different gametes in meiosis." This law states that the two alleles for a heritable character segregate during gamete formation and end up in different gametes. The two alleles separate from each other during formation- thus, an egg or a sperm gets only one of the two alleles that are present in the organism.
A BbGg x bbgg cross yields a phenotypic ratio of approximately 5 black eyes, green skin : 5 orange eyes, white skin : 1 black eyes, white skin : 1 orange eyes, green skin. Which of the following best explains these results?
Mendel's law of independent assortment is being violated. If the genes for eye color and skin color assorted independently, then the outcome of this cross would have been a 1:1:1:1 ratio.
the law of segregation
Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes. Thus, an egg or a sperm gets only one of the two alleles that are present in the organism. This segregation of alleles corresponds to the distribution of homologous chromosomes to different gametes in meiosis.
State Mendel's second law and define it.
Mendel's second law is known as the law of independent assortment. This law states that each pair of alleles separates independently of any other pair of alleles during gamete formation. This law applies to only genes on different, nonhomologous chromosomes or to those far apart on the same chromosome. Genes that are located near each other on the same chromosome tend to be inherited together.
Probability laws govern
Mendelian inheritance
What is always the first amino acid in the new polypeptide?
Methionine because it is the amino acid the start codon (AUG) codes for.
List the two types of eukaryotic cell division
Mitosis Meiosis
Eukaryotic cell division consists of
Mitosis, the division of the genetic material in the nucleus Cytokinesis, the division of the cytoplasm
poly-A tail
Modified end of the 3' end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides.
Missense mutations
Most common type of mutation, a base pair mutation in which the new codon makes sense in that it still codes for an amino acid but for a different amino acid
___ mutations are generally needed for full-fledged cancer; thus the incidence increases with age
Multiple
*Nerves and Neurons are NOT the same thing.
Nerves are bundles of axons (fibers). The axons that comprise a nerve are from many different neurons. Neurons are electrically excitable cells.
In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?
No replication fork will be formed.
A white-eyed female Drosophila is crossed with a red-eyed male Drosophila. Which statement below correctly describes the results?
None of the females will have white eyes. All of the females will have red eyes because they will inherit the dominant red-eye allele from their male parent.
one gene-one protein
Not all proteins are enzymes, so researchers later revised the one gene-one enzyme hypothesis:
Organogenesis
Notochord - stiff dorsal skeletal rod, forms from mesoderm Neural plate 🡪 neural tube🡪 brain and spinal cord Neurulation - forms hollow dorsal nerve chord Somites - blocks of mesoderm arranged along notochord; sign of segmentation
parental types
Offspring with a phenotype that matches one of the parental phenotypes.
The lagging strand is synthesized as
Okazaki fragments, each with an RNA primer
Once it was known that genes exist as parts of chromosomes (T. H. Morgan) the identity of the genetic material had to be determined. What two molecules were candidates for the genetic material?
Once it was known that genes exist as parts of chromosomes, DNA and protein became the candidates for genetic material. "Until the 1940s, the case for proteins seemed stronger, especially since biochemists had identified them as a class of macromolecules with great heterogeneity and specificity of function, essential requirements for the hereditary material. Moreover, little was known about nucleic acids, whose physical and chemical properties seemed far too uniform to account for the multitude of specific inherited traits exhibited by every organism. This view gradually changed as experiments with microorganisms yielded unexpected results. As with the work of Mendel and Morgan, a key factor in determining the identity of the genetic material was the choice of appropriate experimental organisms. The role of DNA in heredity was first worked out while studying bacteria and the viruses that infect them, which are far simpler than pea plants, fruit flies, or humans."
One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant gene, although it may range from mildly to very severely expressed. If a young child is the first in her family to be diagnosed, which of the following is the best explanation?
One of the parents has very mild expression of the gene.
Cross-pollinate
One plant pollinates another plant of another variety. The genetic material from both plants combine and the seeds produced will have traits from both plant varieties; it then becomes a new variety.
How many genes have been found on the human Y chromosome?
Only 78 genes, coding for about 25 proteins
Female reproductive system reproductive cells (gametes)?
Oogenesis 🡪 EGGS
The phytochrome receptor responds to light by
Opening Ca2+ channels, which increases Ca2+ levels in the cytosol Activating an enzyme that produces cGMP
Later work by ___, ____ and ___ identified the transforming substance as DNA
Oswald Avery, Maclyn McCarty, and Colin MacLeod Many biologists remained skeptical, mainly because little was known about DNA
Height is a good example of polygenic inheritance:
Over 180 genes affect height
Telophase and Cytokinesis
Pairs arrives at poles and cell is pinched apart, separating into two cells. Chromosomes become less tightly coiled Nuclear envelopes arise from the fragments of the parent cell's nuclear envelope
dihybrids
Parents that are heterozygous for two characters.
Explain the cause of the genetic disorder Xeroderma Pigmentosum.
People that have xeroderma pigmentosum are extremely sensitive to UV light. The disorder is the result of mutations that affect the nucleotide excision repair pathway. When it doesn't work, thymine dimers and other forms of UV damage remain and aren't repaired. Thus, people with xeroderma pigmentosum develop severe sunburns from a few minutes in the sun and are extremely susceptible to skin cancer unless they avoid the sun.
Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?
Phosphate groups The potential energy stored in the bonds of the phosphates provides the energy for DNA synthesis.
At each step a relay signal is transduced (changed) into a different form via conformational change in a protein. What causes this conformational change to happen to the protein?
Phosphorylation generally causes the conformational change to happen in the protein. At each step, the relay signal is changed into a different form.
etiolation
Plant morphological adaptations for growing in darkness. A potato left growing in darkness produces pale stems, unexpanded leaves, and short roots
Large-scale chromosomal alterations in humans and other mammals often lead to spontaneous abortions (miscarriages) or cause a variety of developmental disorders. ___ tolerate such genetic changes better than animals do.
Plants
List the two places where cell signal receptors are located?
Plasma membrane (cell surface receptors) The cytoplasm/nucleus of target cells (intracellular receptors)
Gap junctions
Points that provide cytoplasmic channels from one cell to another with special membrane proteins. Also called communicating junctions.
Microtubules
Polymers of tubulin that are part of the cytoskeleton Structure and shape for eukaryotic cells They shorten by depolymerizing at their kinetochore ends
light chains
Polypeptide chains that contribute to the structure of an antibody. Two identical light chains and two identical heavy chains, joined by disulfide bridges, form a Y-shaped antibody molecule.
How does aneuploidy differ from polyploidy?
Polyploidy is a condition in which an organism has more than 2 complete sets of chromosomes. Triploidy (3n) is three sets of chromosomes and Tetraploidy (4n) is four sets of chromosomes. "Polyploidy is common in plants, but not animals. Polyploids are more normal in appearance than aneuploids." Aneuploidy involves an abnormal number of a specific chromosome while polyploidy involves an abnormal number of a complete set of chromosomes.
This RNA polymerase synthesizes an RNA primer antiparallel to the template DNA strand.
Primase
asexual reproduction
Process by which a single parent reproduces by itself; Clone
Internal Fertilization
Process in which eggs are fertilized inside the female's body -Sperm deposited in female reprod. tract -Cooperative behavior -Dry environment -Fewer gametes, fewer zygotes 🡪 greater survival
crossing over
Process in which homologous chromosomes exchange portions of their chromatids during meiosis.
Glucagon
Produced in the pancreas; secreted by the alpha cells (which make glucagon) of the pancreatic islet. Released into the interstitial fluid and enters the circulatory system. Releases glucose into the body for energy
Insulin
Produced in the pancreas; secreted by the beta cells (which make insulin) of the pancreatic islets (clusters of endocrine cells). Released into the interstitial fluid and enters the circulatory system. Takes up glucose from the bloodstream to be stored as glycogen
The two types of cell cycle regulatory molecules are:
Protein kinases Cyclins "Many of the kinases that drive the cell cycle are actually present at a constant concentration in the growing cell, but much of the time they are in an inactive form. To be active, such a kinase must be attached to a cyclin, a protein that gets its name from its cyclically fluctuating concentration in the cell. Because of this requirement, these kinases are called cyclin-dependent kinases, or Cdks. The activity of a Cdk rises and falls with changes in the concentration of its cyclin partner.
How are signal transduction pathways turned off?
Protein phosphatases are enzymes that quickly remove phosphate groups from proteins (dephosphorylation). Dephosphorylation inactivates the protein kinases- thus, phosphatases turn off the signal transduction pathway when the initial signal is no longer present. Phosphatases also allow the protein kinases to be available for reuse- the cell is then able to respond again to an extracellular signal.
Possible combinations of sperm and egg can be shown using a
Punnett square A capital letter represents a dominant allele, and a lowercase letter represents a recessive allele
___ is the bridge between genes and the proteins for which they code
RNA
Translation is the
RNA directed synthesis of a polypeptide
The blocking of gene expression by siRNAs is called
RNA interference (RNAi)
Termination of Transcription in Eukaryotes
RNA polymerase II transcribes the polyadenylation signal sequence; the RNA transcript is released 10-35 nucleotides past this polyadenylation sequence
Termination of transcription in eukaryotes
RNA polymerase II transcribes the polyadenylation signal sequence; the RNA transcript is released 10-35 nucleotides past this polyadenylation sequence "In eukaryotes, RNA polymerase II transcribes a sequence on the DNA called the polyadenylation signal sequence, which codes for a polyadenylation signal (AAUAAA) in the pre-mRNA. Then, at a point about 10-35 nucleotides downstream from the AAUAAA signal, proteins associated with the growing RNA transcript cut it free from the polymerase, releasing the pre-mRNA. The pre-mRNA then undergoes processing."
Only when the complete initiation complex has assembled can the
RNA polymerase begin to move along the template strand of the DNA
___ produces a complementary strand of RNA
RNA polymerase moving along the template strand
What is the name of the enzyme that uses the DNA template strand to transcribe a new mRNA strand?
RNA polymerase opens the two strands of DNA and binds to a promoter near the beginning of a gene. The polymerase uses the template strand to make a new and complementary RNA molecule. This enzyme converts DNA into RNA and codes in the 5' to 3' direction.
RNA synthesis is catalyzed by
RNA polymerase, which pries the DNA strands apart and joins together the RNA nucleotides
Primase synthesizes
RNA primer
What name is given to the process in which pre-mRNA is edited into mRNA?
RNA processing RNA processing edits the RNA transcript that has been assembled along a DNA template.
Eukaryotic RNA transcripts are modified through
RNA processing to yield finished mRNA
An egg's cytoplasm contains
RNA, proteins, and other substances that are distributed unevenly in the unfertilized egg
saltatory conduction
Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.
Sutherland suggested that cells receiving signals went through three processes:
Reception, Transduction, Response
Are recessive X-linked alleles expressed in both males and females? Explain.
Recessive X-linked alleles are expressed in both males and females, but X-linked recessive disorders are much more common in males than in females. X-linked genes follow a specific pattern of inheritance. For a recessive X-linked trait to be expressed, either a (1) a female needs two copies of the allele (homozygous) or (2) a male needs only one copy of the allele (hemizygous).
Some human cells divide once every 24 hours. Where in the body might you find cells that divide frequently?
Red blood cells, epithelial (skin cells), stomach lining cells
You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits?
Red shows incomplete dominance over white.
Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot appropriately metabolize the amino acid phenylalanine. This amino acid is not naturally produced by humans. Therefore, the most efficient and effective treatment is which of the following?
Regulate the diet of the affected persons to severely limit the uptake of the amino acid.
Summarize both negative and positive regulation of the Lac Operon. Do so in a manner that is meaningful as well as complete.
Regulation of the Lac operon involves both positive and negative regulation. The lac repressor binds to the operator and blocks the RNA polymerase from binding to the promoter on the DNA. As long as the repressor is bound, transcription of DNA to lac mRNA does not occur. When lactose is present in the cell, it binds to the repressor protein, which changes its shape. Thus, the lac repressor is no longer bound to the operator and RNa polymerase binds to the promoter. Transcription occurs. Thus, more lactose enters the cell and the operon is active until the lactose is no longer present. Regulation of this operon also involves positive regulation. The lac operon is only expressed at a high level when glucose is absent. CAP binds near the promoter (when cAMP, which bind to CAP, levels are high, and this occurs when glucose levels are low) and facilitates the initiation of transcription with RNA polymerase. When cAMP levels are low (bc glucose is high), CAP does not bind to it effectively, and thus, does not turn on the lac promoter. "Regulation of both the trp and lac operons involves negative control of genes because operons are switched off by the active form of the repressor."
What are regulatory genes?
Regulatory genes are the genes that encode regulatory (repressible and inducible) proteins. The regulatory gene is not located on the operon, but located some distance away from it.
Growth factors
Regulatory proteins that ensure that the events of cell division occur in the proper sequence and at the correct rate.
Generally, the relay molecules in a transduction pathway are what type of molecules?
Relay molecules relay a signal from receptor to response (certain information is passed on). They are generally proteins. At each step, the signal is converted into a different form (generally a shape change in the relay protein). Often, this shape change is brought about by phosphorylation.
Female reproductive system: role of LH?
Release of egg (ovulation)
Telomeres
Repeated DNA sequences at the ends of eukaryotic chromosomes.
Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA?
Rosalind Franklin
Finally, the R5P is converted to
RuBP without the addition or loss of carbon atoms.
The cell grows during all three phases of interphase, but chromosomes are duplicated only during the
S phase
Male Anatomy
Scrotum (1) Testes (2) Epididymis (2) Vas deferens (2) Urethra (1) 3 glands Penis (1) -seminiferous tubules
Posterior pituitary
Sends hormones (oxytocin and antidiuretic hormone).
Skin receptors
Sensory organs for touch, pressure, pain, cold, and warmth
What type of mutation causes sickle cell anemia?
Sickle cell anemia is caused by a point mutation of a single nucleotide pair in the gene that encodes the β-globin polypeptide of hemoglobin. This mutation sees the amino acid glutamic acid being replaced with the amino acid valine. Thus, an abnormal protein is produced.
Small interfering RNAs
Similar to miRNA, but formed from longer, double stranded RNA molecules length of 21-23 nucleotides double-stranded inhibit gene expression by degrading homologous mRNA
Metaphase
Sister chromatids are arranged at the metaphase plate
origin of replication
Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.
In incomplete dominance
Situation in which one allele is not completely dominant over another allele the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties
Okazaki fragments
Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.
second messengers
Small, non-protein water soluble molecules or ions that send messages throughout the cells by diffusion.
blastomeres
Smaller cells produced by cleavage during mitotic cell division
Bacterial and eukaryotic ribosomes are somewhat similar but have significant differences.
Some antibiotic drugs specifically target bacterial ribosomes without harming eukaryotic ribosomes
Explain the concept of alternative RNA splicing.
Some introns consist of sequences that regulate gene expression. Furthermore, some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during splicing. This is known as alternative RNA splicing. The splicing pattern in different cells are also different and so the number of different proteins an organism can produce is greater than the amount of genes it has. "Alternative splicing means that the splicing machinery selects certain exons or parts of certain exons differently in a proportion of the molecules that it splices. So it's a way to take a gene and from its primary transcript, generate two or more mRNAs that can encode two or more proteins. The splicing machinery has a choice. It sees this string of exons and it chooses what to join to what. It isn't always product A or product B, you could have some proportion of the molecules choose pathway A and the rest choose pathway B and that is the case with SMN2. If it were to completely skip exon 7, that maybe a lethal change in the absences of SMN1. In reality, it makes some full length protein." "Proteins often have a modular architecture consisting of discrete regions called domains. In many cases, different exons code for the different domains in a protein. Exon shuffling may result in the evolution of new proteins."
Endocrine signaling
Specialized cells release hormone molecules into vessels of the circulatory system, by which they travel to target cells in other parts of the body.
Male reproductive system reproductive cells (gametes)
Spermatogenesis 🡪 SPERM
M checkpoint
Spindle assembly checkpoint. Mitosis will not continue if chromosomes are not properly aligned. Checks for chromosome attachment to the spindle at the metaphase plate
simple neuroendocrine pathway
Stimulus received by sensory neuron which stimulates neurosecretory cell to secrete neurohormone For example, the suckling of an infant stimulates signals in the nervous systems that reach the hypothalamus. Nerve impulses from the hypothalamus trigger the release of oxytocin from the posterior pituitary. This causes the mammary glands to secrete milk
Lymphocytes that mature in the thymus, above the heart, are called ___ , and those that mature in bone marrow are called ___
T cells; B cells
Alfred Hershey and Martha Chase (1952)
T2 bacteriophage (virus) were grown in an isotopic medium so a certain viral component could be labeled. Viruses that were grown in radioactive sulfur had radiolabeled atoms in their proteins (because sulfur is present in proteins and not DNA). VIruses that were grown in radioactive phosphorus had radiolabeled DNA because phosphorus is present in DNA and not proteins. Samples of nonradioactive E. coli cells were allowed to be infected by the protein- and DNA- labeled batches of T2. The two samples were then tested shortly after the onset of infection to see whether protein or DNA had entered the bacterial cells and would thus be able to reprogram them. The phage DNA had entered the host cells but the phage protein did not. Furthermore, when the bacteria were returned to a culture medium, E. coli released phages that contained some radioactive phosphorus. The DNA inside the cell played an ongoing role during the process of infection. The DNA injected by the phage must be the molecule carrying the genetic info that makes the cell produce new viral DNA and proteins
General transcription factors are essential for the transcription of all protein-coding genes. A few bind to the
TATA box within the promoter Many bind to proteins, including other transcription factors and RNA polymerase II
What enzyme is involved in maintaining telomere length and how (what does it add to the ends of chromosomes)?
Telomerase catalyzes the lengthening of telomeres in germ cells. It adds telomeric repeats to the 3' end of the telomere.
What did the Meselson and Stahl experiment prove?
That DNA replication is semi-conservative
p53 gene
The "guardian angel of the genome," p53 is expressed when a cell's DNA is damaged. Its product, p53 protein, functions as a transcription factor for several genes. a tumor-suppressor gene that codes for a specific transcription factor that promotes the synthesis of proteins that inhibit the cell cycle
Is the Calvin cycle a catabolic or anabolic process? Explain
The Calvin cycle is an anabolic process. It builds complex molecules (sugar) from smaller molecules
What is the function of the Calvin cycle?
The Calvin cycle is anabolic- it builds glucose from smaller molecules using ATP and the reducing power of electrons carried by NADPH.
template strand
The DNA strand that provides the template for ordering the sequence of complementary nucleotides in an mRNA transcript.
Where is the G protein located?
The G protein is located on the cytoplasmic side of the membrane. It functions as a molecular switch that is either on or off (depending on which of the guanine nucleotide is attached, GDP or GTP).
What cell organelle contributes to the formation of the cell plate?
The Golgi apparatus contributes to the formation of the cell plate
Where is the HER2 tyrosine-kinase receptor found?
The HER2 tyrosine-kinase is found in tumors and cancer cells
On which chromosome is the SRY gene located and what is its function?
The SRY (sex-determining region on the Y) gene is located on the Y chromosome. This gene is responsible for the development of testes in an embryo.
pleiotropy
The ability of a single gene to have multiple effects. For example, pleiotropic alleles are responsible for the multiple symptoms of certain hereditary diseases, such as cystic fibrosis and sickle-cell disease
Hemophilia
The absence of one or more proteins required for blood clotting When sufferers are injured, bleeding is prolonged because a firm clot forms slowly Bleeding in muscles/joints are painful and can be damaging Sufferers are treated with intravenous injections or the missing protein
Activated G protein is bound to what molecule?
The activated G protein dissociates from the receptor, diffuses across the membrane and then binds to an enzyme (which alters the enzyme's shape & activity). The activated enzyme can trigger the next step leading to a cellular response.
DNA methylation
The addition of methyl groups to bases of DNA after DNA synthesis; may serve as a long-term control of gene expression.
What endocrine gland secretes epinephrine?
The adrenal glands secrete epinephrine (adrenaline). When epinephrine arrives at the liver, it binds to a GPCR (G protein coupled receptor) in the plasma membrane of target cells. When this binding occurs, a cascade of events occur. "When epinephrine reaches the liver, it binds to a G protein-coupled receptor in the plasma membrane of target cells. The binding of hormone to receptor triggers a cascade of events involving synthesis of cyclic AMP (cAMP) as a short-lived second messenger. Activation of protein kinase A by cAMP leads to activation of an enzyme required for glycogen breakdown and inactivation of an enzyme necessary for glycogen synthesis. The net result is that the liver releases glucose into the bloodstream, providing the fuel you need to chase the departing bus."
Chargaff's rules
The base composition of DNA varies between species In any species the number of A and T bases is equal and the number of G and C bases is equal
Thymine
The base that pairs with Adenine in DNA. Pyrimidine.
Guanine
The base that pairs with Cytosine in DNA. Purine.
Cytosine
The base that pairs with Guanine with DNA. Pyrimidine.
Adenine
The base that pairs with Thymine in DNA. Purine.
How does the process of transcription/translation differ in prokaryotes and eukaryotes?
The basic mechanisms of trasncription/translation are similar in prokaryotes and eukaryotes but the major difference stems from the prokaryotes' lack of nuclei. Their DNA isn't separated by nuclear membranes from ribosomes and other equipment that synthesize protein. Due to the lack of compartmentalization, translation of an mRNA begins while it is still undergoing transcription. In eukaryotes, the nuclear envelope separates transcription (occurs in the nucleus and transports mRNA to the cytoplasm) from translation (occurs in the cytoplasm).
What triggers the first step of a signal transduction pathway?
The binding of a specific ligand to a receptor in the plasma membrane triggers the first step of a signal transduction pathway. The signal-activated receptor then activates another molecule, which activates another molecule- this process goes on until the protein that produces a cellular response is activated.
de-etiolation
The changes a plant shoot undergoes in response to sunlight; also known informally as greening.
It may be possible to avoid passing along mitochondrial disorders. Explain?
The chromosomes from the egg of an affected mother could be transferred to an egg of a healthy donor, generating a "two-mother" egg. This egg could then be fertilized by sperm from the prospective father and transplanted to the womb of the prospective mother.
transcription initiation complex
The completed assembly of transcription factors and RNA polymerase bound to a promoter.
How are control signals within the cell transmitted? (Hint: Consider how cells communicate)
The control signals are transmitted within the cell by means of signal transduction pathways. "Animal cells generally have built-in stop signals that halt the cell cycle at checkpoints until overridden by go-ahead signals. Many signals registered at checkpoints come from cellular surveillance mechanisms inside the cell. These signals report whether crucial cellular processes that should have occurred by that point have in fact been completed correctly and thus whether or not the cell cycle should proceed. Checkpoints also register signals from outside the cell, as we will discuss later. Three major checkpoints are found in the G1, G2, and M phase."
In the disease multiple sclerosis, the myelin sheaths harden and deteriorate. How would this affect nervous system function?
The deterioration of myelin sheaths would affect the speed of action potentials. Nervous system function would thus be inhibited and sufferers would have impaired motor functions.
Acrosomal reaction
The discharge of hydrolytic enzymes from the acrosome, a vesicle in the tip of a sperm, when the sperm approaches or contacts an egg.
What commonly held idea was rendered obsolete by the discovery of ribozymes?
The discovery of ribozymes (catalytic RNA molecules) made the idea that all biological catalysts are proteins obsolete.
What molecule facilitates the attachment of an amino acid to the tRNA molecule?
The enzyme aminoacyl-tRNA synthetase facilitates the attachment of an amino acid to a tRNA molecule and makes sure that both molecules are a match for each other. "The correct matching up of tRNA and amino acid is carried out by a family of related enzymes called aminoacyl-tRNA synthetases."
Evolutionary Significance of Altered DNA Nucleotides
The error rate after proofreading and repair is low but not zero Sequence changes may become permanent and can be passed on to the next generation These changes (mutations) are the source of the genetic variation upon which natural selection operates and are ultimately responsible for the appearance of new species
differential gene expression
The expression of different sets of genes by cells with the same genome.
How does recombination frequency relate to the distance between genes on a chromosome?
The farther apart two genes are (the more distance they have between them), the higher the probability that a crossover will occur between them. The recombination frequency is higher.
What did Thomas Hunt Morgan conclude after experimenting with wild type and mutant fruit flies? Be sure to review Morgan's experiment.
The first solid evidence associating a specific gene with a specific chromosome came in the early 1900s from the work of Thomas Hunt Morgan. His early experiments provided convincing evidence that the chromosomes are the location of Mendel's heritable factors. Morgan identified wild type, or regular phenotypes that were commonly seen in the fly populations. Mutant phenotypes were the traits alternative to the wild type- the first mutant he discovered was a fly with white eyes instead of red eyes (wild type). In one experiment, Morgan mated male flies with white eyes (mutant type) with female flies with red eyes (wild). The F1 generation all had red eyes (wild). The F2 generation had a 3:1 red to white eye ratio, but only the males had white eyes. He hypothesized that the white-eyed mutant allele must be then located on the X chromosome; this finding supported the chromosome theory of inheritance.
Archibald Garrod
The first to suggest that genes dictate phenotypes through enzymes that catalyze specific chemical reactions in the cell., Reported Alkaptonuria as the first human example of what is now known as Mendelian inheritance. He thought symptoms of an inherited disease reflect an inability to synthesize a certain enzyme. Cells synthesize and degrade molecules in a series of steps, a metabolic pathway
A life cycle is the
The generation-to-generation sequence of stages in the reproductive history of an organism.
Explain the statement - "The genetic code is nearly universal."
The genetic code is nearly universal and is shared by both simple and complex organisms. RNA codons are generally translated into the same amino acid in all organisms who have had their genetic code examined. Genes can still be transcribed and translated after being transplanted to other species. "Exceptions to the universality of the genetic code include translation systems in which a few codons differ from the standard ones. Slight variations in the genetic code exist in certain unicellular eukaryotes and in the organelle genes of some species. Despite these exceptions, the evolutionary significance of the code's near universality is clear. A language shared by all living things must have been operating very early in the history of life—early enough to be present in the common ancestor of all present-day organisms. A shared genetic vocabulary is a reminder of the kinship that bonds all life on Earth."
Explain the following statement - "The genetic code is redundant but not ambiguous."
The genetic code is redundant because some of its codons specify the same amino acid; for example, GAA and GAG both code for glutamic acid. However, neither of the codons codes for any other amino acid- thus, there is no ambiguity in the genetic code. "The redundancy in the code is not altogether random. In many cases, codons that are synonyms for a particular amino acid differ only in the third nucleotide base of the triplet."
How does recombination frequency relate to the distance between genes on a chromosome
The greater the frequency of recombination (segregation) between two genetic markers, the further apart they are assumed to be. Conversely, the lower the frequency of recombination between the markers, the smaller the physical distance between them.
Explain how a test cross is conducted.
The individual is bred with a homozygous recessive individual (for ex, rr). If any offspring display the recessive phenotype (rr), the parent must be heterozygous (because there an r must exist in both parents for it to result in a recessive offspring).
Initiation of Translation and mRNA Degradation
The initation of translation of selected mRNAs can be blocked by regulatory proteins that bind to sequences or structures of the mRNA. Alternatively, tranlation of all mRNAs in a cell may be regulated simultaneously. For example, translation initiation factors are simultaneously activated in an egg following fertilization. The life span of mRNA molecules in the cytoplasm is a key to determining protein synthesis. Eukaryotic mRNA is more long lived than prokayrotic mRNA. Nucleotide sequences that influence the lifespan of mRNA in eukaryotes reside in the untranslated region (UTR) at the 3'end of the molecule.
primary transcript
The initial mRNA transcript that is transcribed from a protein coding gene prior to processing. Also called pre-mRNA.
Summarize regulation by the lac Operon
The lac operon consists of a promoter, an operator and the 3 genes that encode enzymes that metabolize lactose. A repressor is bound to the operator when lactose is absent; transcription of the lactose genes, thus, does not occur, because it is blocked. When lactose is present, allolactose binds to the repressor, and prevents it from binding to the operator. Transcription commences. When glucose is present, cAMP is low, which means that CAP is inactive; transcription occurs, but the RNA polymerase is not as efficient performing transcription without CAP's aid. Thus, transcription levels are low. When glucose is absent, cAMP levels are high, which means that CAP is active and that transcription occurs steadily at a high level.
Summarize regulation by the lac operon when glucose is present and lactose is present
The lac repressor is released from the operator due to the presence of allolactose (the inducer). cAMP levels are also low because glucose is present and, consequently, CAP remains inactive and does not bind to DNA, where it would otherwise aid in transcription. Transcription occurs, but only at a low level.
Summarize regulation by the lac operon when glucose is absent and lactose is present
The lac repressor is released from the operator due to the presence of allolactose (the inducer). cAMP levels are high because glucose is absent and, thus, CAP is active and bound to the DNA. CAP helps RNA polymerase to bind to the promoter; this results in high levels of transcription.
Summarize the synthesis of the lagging strand during DNA replication.
The lagging strand is oriented in the 5' to 3' direction (away from the replication fork). It is replicated discontinuously, with Okazaki fragments. Because DNA is replicated from the 5' to 3' direction, the lagging strand is replicated differently. Numerous RNA primers are made by primase and bind to various places along the strand. Okazaki fragments (pieces of DNA) are added to the strand in the 5' to 3' direction. DNA polymerase works in the direction away from the replication fork. The Okazaki fragments are joined together by DNA ligase.
Which of the following steps occurs last in the initiation phase of translation?
The large ribosomal subunit joins the complex This step occurs after the 5' mRNA is bound by the ribosome and the start codon is bound by an aminoacyl tRNA.
Summarize the synthesis process of the leading strand during DNA replication.
The leading strand is oriented towards the replication fork in the 3' to 5' direction. It is replicated continuously. A primer (a short piece of RNA) binds to the end of the leading strand binds to the end of the leading strand- it acts as the starting point for DNA synthesis. DNA polymerase binds to the strand and then moves along it, adding new nucleotide bases that are complementary to the strand of DNA (in the 5' to 3' direction).
Do the levels of cyclins vary?
The levels of cyclins vary and their concentration cyclically fluctuates.
Are the Light reactions catabolic or anabolic processes? Explain
The light reactions are catabolic. They split complex molecules (H2O) into smaller molecules (oxygen and hydrogen).
Summarize the Light reactions and the Calvin cycle
The light reactions occur in the thylakoid membranes. They convert light energy to the chemical energy of ATP and NADPH. Light reactions split H2O and release O2 into the environment. The Calvin cycle occurs in the stroma. It uses ATP and NADPH to convert CO2 to G3P (a sugar). It returns ADP, inorganic phosphate and NADPH+ to the light reactions (to be converted again into ATP and NADPH).
The relationships between the light reactions and the Calvin cycle?
The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle returns ADP, i, and NADP+ to the light reactions
phosphorylation
The metabolic process of introducing a phosphate group into an organic molecule.
RNA processing
The modification of mRNA before it leaves the nucleus that is unique to eukaryotes.
Positional information
The molecular cues that control pattern formation.
sister chromatid cohesion
The name of the attachment of two sister chromatids. Protein complexes (cohesins) are responsible for this, they adhere two sister chromatids together.
leading strand
The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.
DNA is a self-replicating molecule. What accounts for this important property of DNA?
The nitrogenous bases of the double helix are paired in specific combinations: A with T and G with C. Because of the specificity of the pairing of the nitrogenous bases, each strand of the double helix specifies the matching sequence of bases on the other strand. During replication, when the strands separate, each strand serves as a template for the replication of other strand.
Why is the non-template strand called the coding strand?
The non-template strand is called the coding strand because the codons on this strand are complementary to the template strand (like the mRNA is) and so is identical to the sequence of mRNA (except for the DNA strand having thymine while the mRNA strand has uracil).
synapsis
The pairing of two homologous chromosomes; DNA from one non sister chromatid is joined to the corresponding segment of another
Determination
The point during development at which a cell becomes committed to a particular fate due to cytoplasmic effects or to induction by neighboring cells.
When the wave of depolarization arrives at the synaptic terminal, calcium ion channels open. What occurs to the synaptic vesicles as the Ca2+ level increases?
The presynaptic nerve cell synthesizes and packages neurotransmitter molecules in synaptic vesicles located in the synaptic terminal. When an action potential occurs, the neurotransmitter is released. It then diffuses across the synaptic cleft and is received by the postsynaptic cell (the neurotransmitter binds to its receptor sites on ligand gated ion channels of the postsynaptic cell). The ion channels then open which generates a postsynaptic potential (either excitatory or inhibitory). As the Ca2+ level increases, the synaptic vesicles release acetylcholine (a neurotransmitter). The molecules of acetylcholine diffuse from the presynaptic terminal across the synaptic cleft and bind to ligand-gated sodium channels. The channels open and sodium diffuses into the cell- the membrane potential is more positive. When the potential reaches threshold, an action potential is produced.
antigen presentation
The process by which an MHC molecule binds to a fragment of an intracellular protein antigen and carries it to the cell surface, where it is displayed and can be recognized by a T cell.
clonal selection
The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for the stimulating antigen.
morphogenesis
The process by which an organism takes shape and the differentiated cells occupy their appropriate locations.
External Fertilization
The process by which the female lays eggs and the male fertilizes them once they are outside of the female -Egg shed by female, fertilized by male in water -Environmental cues / courtship behavior -Large # gametes 🡪 low survival Eg. fish, amphibians
depolarization
The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.
Contrast the primary immune response with the secondary immune response.
The production of effector cells from a clone of lymphocytes during first exposure to an antigen is the basis for the primary immune response, which peaks about 10-17 days after the initial exposure. During this time, selected B cells and T cells give rise to their effector forms. A clone of lymphocytes is formed. The secondary immune response is a hallmark of adaptive immunity. This response relies on the reservoir of T and B memory cells that are generated following initial exposure to an antigen.
cell cycle
The regular sequence of growth and division that cells undergo the life of a cell from formation to its own division
RNA splicing
The removal of introns and joining of exons in eukaryotic RNA, forming an mRNA molecule with a continuous coding sequence; occurs before mRNA leaves the nucleus.
Just like toppling dominoes in a row, either the threshold of depolarization will be reached and an action potential will be generated, or the threshold will not be reached and no wave will occur. What is this response to stimulus called?
The response to stimulus is called an "all-or-none" response. Once the threshold is reached, an action potential will be generated. If the threshold is not reached, no action potential will be generated. Hence, "all-or-none."
Genetics
The scientific study of heredity and variation
Prometaphase
The second stage of mitosis, in which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the chromosomes. Each of the two chromatids of a chromosome has a kinetochore Microtubules from the spindle interact with the condensed chromosomes
The sequential events of the cell cycle are regulated by the cell cycle control system. Where are the signal molecules for this control system located?
The signal molecules for this control system are located in the cytoplasm.
evolutionary developmental biology
The study of developmental biology to shed light on evolutionary dynamics
Griffith's experiments with S. pneumoniae were significant because they showed that traits could be transferred from one organism to another. What else did he find that was significant?
The transferred traits were heritable. The fact that offspring of transformed bacteria also showed the pathogenic trait meant that the transforming agent had to be involved with the genetic material.
epigenetic inheritance
The transmission of a heritable pattern of gene expression from one cell to its progeny that does not involve altering the nucleotide sequence of the DNA.
Parental (P) generation
The true-breeding parents that cross-pollinated to produce filial generations
What are the two groups of regulatory proteins, how do they function and where does each bind to the operon?
The two groups of regulatory proteins are repressors and inducers. Repressors prevent gene transcription by binding to the operator to block RNA polymerase- it is the product of a separate regulatory gene. A repressible operon is usually on, and the binding of a repressor to its operator shuts transcription off. Inducers are molecules that inactivate repressors in order to turn operons on. An inducible operon is usually turned off (because a repressor is bound to it), and the binding of the inducer to the repressor inactivates it, and turns on transcription. Inducible enzymes usually function in catabolic (degradative) pathways where their synthesis is induced by a chemical signal while repressible enzymes usually function in anabolic (constructive) pathways where their synthesis is repressed by high levels of the end product.
What are the two intracellular responses in the liver to epinephrine? How do these help the body deal with short-term stress?
The two intracellular responses in the liver as a result of epinephrine are the inhibition of glycogen synthesis and the promotion of glycogen breakdown. Rather than producing glycogen, the liver breaks it down. This releases energy, in the form of glucose, into the organism, powering them to survive a "fight-or-flight" scenario.
Lymphocytes
The two types of white blood cells that are part of the body's immune system: B lymphocytes form in the bone marrow and release antibodies that fight bacterial infections; T lymphocytes form in the thymus and other lymphatic tissue and attack cancer cells, viruses, and foreign substances.
membrane potential
The voltage across a cell's plasma membrane.
reading frame
The way a cell's mRNA-translating machinery groups the mRNA nucleotides into codons
Explain the flow of info from gene to protein based on the triplet code
The words of a gene are transcribed into complementary nonoverlapping three-nucleotide words of mRNA. These words are then translated into a chain of amino acids, forming a polypeptide
Centrioles
They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers.
Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?
They cannot repair thymine dimers.
Nüsslein-Volhard and Wieschaus experiment.
They created mutants, conducted breeding experiments, and looked for corresponding genes Many of the identified mutations were embryonic lethals, causing death during embryogenesis. They found about 120 genes essential for normal segmentation
Why do neurons and some other specialized cells divide infrequently?
They have been shunted into G0.
Why is it difficult to observe individual chromosomes with a light microscope during interphase?
They have uncoiled to form long, thin strands.
Nonkinetochore microtubules
They interdigitate at the cell's equator and then move apart, causing the cell to elongate.
Several characteristics make fruit flies a convenient organism for genetic studies:
They produce many offspring A generation can be bred every two weeks They have only four pairs of chromosomes
Purpose of telomeres:
They protect the ends of our chromosomes by forming a cap, much like the plastic tip on shoelaces. Each time DNA replicates chromosomes shorten by 25-200 bases Addition of these repeat sequences ensures that genes aren't lost (only telomere sequences are lost -phew!) But as we age more and more telomeres are lost (yikes) Once the telomere becomes too short the chromosome will no longer be replicated and hence triggers cell death called apoptosis. (oh no!)
When a stimulus is applied, ion channels will open. If positively charged ions flow in, the membrane is said to depolarize. If depolarization causes the membrane potential to drop to a critical value, a wave of depolarization will follow. What is this critical value called?
This critical value is known as threshold. Ion channels are voltage-gated and so they open or close when threshold is passed. Thus, action potentials arise.
How does feedback inhibition in gene expression benefit the organism?
This feedback inhibition benefits the organism by conserving its resources. When there is too much of the substance in the cell, the production of it is halted. Thus, the feedback inhibition ensures that the substance is only made when the cell is in need of it, and energy sources are conserved.
Where does RNA polymerase attach to initiate transcription?
To initiate transcription, RNA polymerase binds to a region on the gene known as a promoter. The promoter consists of DNA sequence that let the polymerase attach to the DNA.
This enzyme untwists the coils that occur in the DNA as it is being unwound into a single-stranded template.
Topoisomerase
What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
Traits are inherited in discrete units, and are not the results of "blending."
___ is the first stage of gene expression
Transcription
What comprises a transcription initiation complex?
Transcription factors and RNA polymerase II bound to a promoter
Summarize regulation by the lac operon when glucose is present and lactose is absent
Transcription of the lac operon does not occur because the lac repressor remains bound to the operator (if lactose was present, it would bind to allolactose, another form of lactose) and prevents RNA polymerase binding to the promoter and start transcription. cAMP levels are low because glucose levels are high and thus, CAP (regulated by cAMP) is inactive and cannot bind to the DNA to promote transcription. No transcription occurs.
The only known viable monosomy in humans
Turner syndrome
Which type of diabetes is correlated with obesity?
Type 2
Mutant cell cycle-inhibiting pathway
UV light leads to DNA damage in genome Mutation occurs Defective or missing transcription factor Inhibitory protein absent Cell cycle is not inhibited (increased cell division)
Rosalind Franklin (1952)
Used X-ray crystallography to produce a picture of the DNA molecule structure. Her images of DNA allowed Watson to deduce that DNA was helical. He also deduced the width of the helix and the spacing of the nitrogenous bases.
genomic imprinting
Variation in phenotype depending on whether an allele is inherited from the male or female parent.
What is the function of the Golgi with respect to cell plate formation?
Vesicles from the apparatus, which are carrying phospholipids used to make the cell membrane, and sugars, used to make the cell wall, are delivered to the cell and assembled along a network of spindle fibers that form in the middle of the cell. The cell plate is produced.
Where are the receptors for the water-soluble proteins found? Explain this difference for the two types of hormones.
Water-soluble hormones are unable to pass directly through the plasma membrane. Thus, their receptors are found directly on the outer surface of the cell's membrane. When water-soluble hormones bind to their cell surface receptors, a G protein is activated. Adenylate cyclase is activated which converts ATP to cAMP (second messenger), amplifying the signal of the receptor-hormone complex. cAMP activates kinase proteins which then activate other enzymes through the use of phosphorylation reactions (the response). The receptors for lipid-soluble hormones are found in the cell while those for water-soluble hormones are found on the cell.
Explain the concept of semiconservative replication.
When a double helix replicates, each daughter molecules will have one old strand (converseved from the parent molecule) and one newly made strand.
What is the result when a prokaryote or unicellular eukaryote divides?
When a prokaryote or unicellular eukaryote divides, they reproduce; the process of cell division is called binary fission. In this process, the chromosomes are replicated (the origin of replication is duplicated). The origins move to opposite poles which results in the chromosomes moving apart. A septum (new dividing wall) is formed and the plasma membrane pinches inward, dividing the cell into two.
What happens when a signaling molecule (ligand) binds to an ion channel receptor?
When a signaling molecule (ligand) binds to the receptor protein, the gate opens or shuts, allowing or blocking the flow of ions (like Na+ or Ca2+) through a channel in the receptor.
Cell communication is stated as evidence for the evolutionary relatedness of life? Explain.
When biologists study cell signalling, they discover that all types of cells possess similar mechanisms for cellular regulation and communication, no matter how diverse the species is. Thus, there is believed to be an evolutionary kinship between these mechanisms.
How does codominance differ from incomplete dominance? (In which do both alleles show their effects? In which do both alleles blend their effects?)
When codominance occurs, both alleles are expressed. An example is seen in blood type AB. Blood cells present both A and B proteins. When incomplete dominance occurs, both alleles are "blended" and the phenotype of the offspring is somewhere between the phenotypes of the parents.
If positively charged ions flow out, the difference in charge between the two sides of the membrane becomes greater. What is the increase in the magnitude of the membrane potential called?
When gated K+ channels open, K+ is diffused out- this makes the inside of the cell more negative. This increase in magnitude of the membrane potential is called hyperpolarization.
Steps of Tyrosine-Kinase receptors signaling
When signaling molecules bind to RTKs, they cause neighboring RTKs to associate with each other, forming cross-linked dimers. Cross-linking activates the tyrosine kinase activity in these RTKs through phosphorylation — specifically, each RTK in the dimer phosphorylates multiple tyrosines on the other RTK. This process is called cross-phosphorylation.
When does G protein become activated?
When the appropriate ligand binds to the extracellular side of the receptor, it is activated and changes shape. Its cytoplasmic side then binds an inactive G protein which causes a GTP to displace the GDP. this activates the G protein.
describe how binary fission differs from mitosis.
While binary fission and mitosis are similar in a way (they both replicate their chromosomes), they have various differences; in binary fission, a mitotic spindle doesn't form like it does in mitosis (this means binary fission is a much faster process). Furthermore, replication, in binary fission, occurs at the same time as separation- the chromosomes in binary fission do not separate and the cytoplasm is not divided (like in mitosis cytokinesis).
Why does a hormone elicit a response only with target cells?
While hormones are circulated throughout the entire body, only target cells are affected by them because only targets have receptors that would allow them to bind to the hormone.
Sex reversal in a sequential hermaphrodite (wrasses)
Wrasses (reef fish) born female, but oldest, largest individuals complete their lives as males.
In an unfertilized egg (ovum), the sex chromosome is
X
The sex chromosomes, which determine the sex of the individual, are called
X and Y
Morgan reasoned that the white-eyed mutant allele must be located on the
X chromosome
How do X chromosomes differ from Y chromosomes?
X chromosomes have sex-linked genes for many characters that are unrelated to sex; many sex-linked genes on the Y chromosome are related to sex determination, on the other hand. The Y chromosome determines the sex of the baby; its presence means that the offspring will be male.
In a sperm cell, the sex chromosome may be either
X or Y
How would the genotype for a female carrier of an X-linked recessive trait be written?
XNXn. For the female to express the X-linked recessive trait, they would need two copies of the allele; in this case, they have only one copy and do, thus, not express the trait. Instead, they are carriers because, when mating with another individual who has a similar carrier phenotype, they may pass on the trait to their offspring.
Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
X^NX^n and X^NY
Each chromosome has hundreds or thousands of genes (except the
Y chromosome)
Genes on the Y chromosome are called
Y-linked genes; there are few of these
Each B cell antigen receptor is a
Y-shaped molecule with two identical heavy chains and two identical light chains
The yeast Saccharomyces cerevisiae has two mating types, which are?
a and α
Cell-cell recognition
a cell's ability to distinguish one type of neighboring cell from another
Flattened into one plane to reveal its base pairing, a tRNA molecule looks like
a cloverleaf
Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height?
a combination of polygenic inheritance and environmental factors
More than _____ and other proteins participate in DNA replication
a dozen
When an antigen binds a B cell, the cell takes in
a few foreign molecules by receptor-mediated endocytosis
Insertion or deletion of nucleotides may alter the reading frame, producing
a frameshift mutation
Nitric oxide
a gas released by the endothelial cells to promote blood flow
the lac operon
a gene system whose operator gene and three structural genes control lactose metabolism in E. coli
dominant trait
a genetic factor that blocks another genetic factor
recessive trait
a genetic factor that is blocked by the presence of a dominant factor
A linkage map is a
a genetic map of a chromosome based on recombination frequencies
Each tRNA molecule enables translation of
a given mRNA codon into a certain amino acid
Operon model
a group of genes is regulated and expressed together as a unit mechanism for control of gene expression in bacteria
When a steroid hormone binds to its cytosolic receptor,
a hormone-receptor complex forms that moves into the nucleus
Mutations in the ras gene can lead to production of
a hyperactive Ras protein and increased cell division
Humans and other mammals have two types of sex chromosomes:
a larger X chromosome and a smaller Y chromosome
During RNA processing a(n) _____ is added to the 3' end of the RNA.
a long string of adenine nucleotides
Normally, only female cats have the tortoiseshell phenotype because
a male inherits only one allele of the X-linked gene controlling hair color.
Tuberculosis kills more than
a million people a year
dimer
a molecule or molecular complex consisting of two identical molecules linked together.
The F1 offspring produced in this cross were monohybrids, heterozygous for one character. A cross between such heterozygotes is called
a monohybrid cross
Synaptic signaling
a nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell
Synaptic signaling occurs in the animal nervous system when
a neurotransmitter is released in response to an electric signal
In nucleotide excision repair,
a nuclease cuts out and replaces damaged stretches of DNA
The fact that males and females inherit a different number of X chromosomes leads to
a pattern of inheritance different from that produced by genes located on autosomes
A gene can be defined as
a region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule
Complete dominance
a relationship in which one allele is completely dominant over another occurs when phenotypes of the heterozygote and dominant homozygote are identical
A negative feedback loop inhibits
a response by reducing the initial stimulus, thus preventing excessive pathway activity
During the refractory period after an action potential,
a second action potential cannot be initiated
After fertilization, the Drosophila embryo develops into
a segmented larva with three larval stages The larva then forms a pupa, which undergoes metamorphosis into the adult fly
The repressor is the product of a
a separate regulatory gene, located some distance from the operon itself
triplet code
a series of nonoverlapping, three-nucleotide words A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.
The binding of a mating factor at the cell surface initiates
a series of steps called a signal transduction pathway
Often the initial transduction of the signal
a shape change in a receptor
A cluster of functionally related genes can be coordinately controlled by
a single "on-off switch"
A genome can consist of a
a single DNA molecule (common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells)
A tRNA molecule consists of
a single RNA stand that is only about 80 nucleotides long
In asexual reproduction
a single individual passes all of its genes to its offspring without the fusion of gametes
Genomic imprinting may affect only
a small fraction of mammalian genes
The mitotic spindle is
a structure made of microtubules that controls chromosome movement during mitosis
Different body cells can respond differently to the same peptide hormones because
a target cell's response is determined by the components of its signal transduction pathways
Antigens
a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies. proteins unique to the pathogen
meiosis
a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores. a special type of division that can produce sperm and egg cells
Chemical mutagens fall into
a variety of categories Most carcinogens (cancer-causing chemicals) are mutagens, and most mutagens are carcinogenic
The release factor causes the addition of
a water molecule instead of an amino acid This reaction releases the polypeptide, and the translation assembly comes apart
Explain how an action potential is transmitted from one cell to another across a synapse.
a. An action potential arrives. The plasma membrane is depolarized. b. Due to the depolarization, voltage-gated channels are opened. c. There is an influx of Ca2+ (calcium ions). d. The increased Ca2+ concentration means synaptic vesicles fuse with the plasma membrane. e. Neurotransmitter is released into the synaptic cleft. f. The neurotransmitter binds to ligand-gated ion channels in the postsynaptic membrane. The channels open, due to the binding of the neurotransmitter to the channel, and the action potential (Na+ and K+) diffuses through.
Totipotent cells
able to differentiate into all cell types, including the three germ layers and placental structures capable of developing into all the different cell types
Conversion of a proto-oncogene to an oncogene can lead to
abnormal stimulation of the cell cycle
Over time, an untreated HIV infection not only avoids the adaptive immune response, but also
abolishes it
In histone acetylation,
acetyl groups are attached to positively charged lysines (amino acid) in histone tails This appears to open up the chromatin structure, thereby promoting the initiation of transcription
Here is a list of several of the major neurotransmitters. You are not expected to know their actions or secretion sites, but you should recognize that they are neurotransmitters.
acetylcholine, epinephrine, norepinephrine, dopamine, serotonin, GABA, glutamate, glycine, substance P, endorphins, and nitric oxide.
Local regulators are molecules that
act over short distances, reaching target cells solely by diffusion
If a depolarization shifts the membrane potential sufficiently, it results in a massive change in membrane voltage called an
action potential
What is the wave of depolarization called?
action potential
Inactivated Na+ channels behind the zone of depolarization prevent the
action potential from traveling backwards
Changes in membrane potential are called
action potentials
In worms and other organisms, apoptosis is triggered by signals that
activate a cascade of "suicide" proteins in the cells programmed to die
This binding of a mature lymphocyte to an antigen initiates events that
activate the lymphocyte
Antigen receptors on the surface of helper T cells bind to the antigen and the class II MHC molecule; then cytokine signals are exchanged between the two cells. The helper T cell is
activated, proliferates, and forms a clone of helper T cells, which then activate the appropriate B cells
When the level of oxygen in blood falls, NO
activates an enzyme that results in vasodilation, increasing blood flow to tissues
The MPF protein complex turns itself off by
activating a process that destroys cyclin components
The humoral response begins with
activation of the B cells
Pattern-recognition receptors on leukocytes recognize and bind to unique molecules on the pathogens, such as the amino acid N-formylmethionine in bacteria. This receptor binding leads to
activation of the innate immune response.
By itself, the lac repressor is
active and switches the lac operon off
Sleep is an
active state for the brain
ligand-gated ion channel receptor
acts as a gate when the receptor changes shape
vertebrates also have ____ immunity
adaptive
Antigens are artificially introduced into the body to generate
adaptive immune response and memory cell formation
Spleen, lymphatic ducts and thymus are components of the
adaptive immune system
The frequency of certain cancers increases when
adaptive immunity is inactivated
In reducing 3-PGA to G3P (Phase 2), there is no
addition or removal of carbon atoms
Some target genes for MyoD (protein) encode
additional muscle-specific transcription factors
Insertions and deletions are
additions or losses of nucleotide pairs in a gene
After a tautomeric shift in adenine...
adenine bonds with cytosine Adenine can still form bonds, but it now bonds with cytosine instead of the usual thymine.
In Engelmann's experiment, he used
aerotactic (oxygen-seeking) bacteria to determine which wavelengths of visible light were most effective in driving the reactions of photosynthesis in green algae
Some defects in mitochondrial genes prevent cells from making enough ATP and result in diseases that
affect the muscular and nervous systems For example, mitochondrial myopathy and Leber's hereditary optic neuropathy
The adaptive immune response is activated
after the innate response and develops more slowly
A biofilm is an
aggregation of bacterial cells adhered to a surface
It has been proposed that the shortening of telomeres is connected to
aging
Innate immunity is found in
all animals and plans; both invertebrates and vertebrates
The discovery of ribozymes rendered obsolete the belief that
all biological catalysts were proteins
An example of an internal signal is that cells will not begin anaphase until
all chromosomes are properly attached to the spindle at the metaphase plate. This mechanism ensures that daughter cells have the correct number of chromosomes
When Mendel crossed contrasting, true-breeding white- and purple-flowered pea plants,
all of the F1 hybrids were purple
What enzyme catalyzes the attachment of an amino acid to tRNA?
aminoacyl-tRNA synthetase This enzyme matches a particular tRNA with a particular amino acid.
Enzyme cascades
amplify the cell's response to the signal At each step, the number of activated products can be much greater than in the preceding step
Generation and experience of emotions involve many brain structures, including the
amygdala, hippocampus, and parts of the thalamus These structures are grouped as the limbic system
The structure most important to the storage of emotion in the memory is the
amygdala, a mass of nuclei near the base of the cerebrum
stimulatory protein
an RNA polymerase II transcription factor in vertebrates; binds to DNA in regions rich in G and C residues; a general promoter-binding factor necessary for the activation of many genes.
Offspring with aneuploidy have
an abnormal number of a particular chromosome
The repressor can be in
an active or inactive form, depending on the presence of other molecules
Testosterone is an example of a chemical signal that affects the very cells that synthesize it, the neighboring cells in the testis, along with distant cells outside the gonads. Thus, testosterone is an example of
an autocrine signal, a paracrine signal, and an endocrine signal.
At the site where the action potential is generated (usually the axon hillock),
an electrical current depolarizes the neighboring region of the axon membrane
In 1953, James Watson and Francis Crick introduced what?
an elegant double-helical model for the structure of deoxyribonucleic acid, or DNA
Adenylyl cyclase
an enzyme in the plasma membrane, converts ATP to cAMP in response to an extracellular signal
Insects' first barrier to pathogens
an exoskeleton made of chitin
In a positive-feedback system where hormone A alters the amount of protein X,
an increase in A always produces an increase in X, which results in an increase in A.
hyperpolarization
an increase in the membrane potential of a cell, relative to the normal resting potential
Repressible enzymes usually function in
anabolic pathways; their synthesis is repressed by high levels of the end product
Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?
anaphase I of meiosis
Cytokinesis begins during
anaphase or telophase, and the spindle eventually disassembles
Nondisjunction of sex chromosomes produces a variety of
aneuploid conditions
Polyploids are more normal in appearance than
aneuploids
By the time of the Cambrian explosion more than 500 million years ago, specialized systems of neurons had appeared that enable
animals to sense their environments and respond rapidly
The G protein and receptor typically work together with
another protein, usually an enzyme.
Body axes
anterior-posterior, dorsal-ventral, left-right
Interfering with the signaling pathways used in quorum sensing may be a promising approach as an alternative to
antibiotic treatment
Humoral response:
antibodies defend against infection in body fluids
In artificial passive immunization,
antibodies from an immune animal are injected into a non immune animal
Mutant tetraploid plants
are unable to interbreed with a diploid plant
Linked genes do not
assort independently
At the DNA level, a cancerous cell is usually characterized by
at least one active oncogene and the mutation of several tumor-suppressor genes
Cytokinesis usually occurs
at the same time as telophase forming two haploid daughter cells (meiosis)
To become active, a kinase must be
attached to a cyclin
The protruding 3' end of the tRNA acts as an ________ ___________ __________ ________
attachment site for an amino acid
Peptides and proteins function in innate defense by
attacking pathogens or impeding their reproduction
Engelmann found that some wavelengths of light
attracted more bacteria, suggesting that these wavelengths drive more photosynthesis than others.
The remaining 22 pairs of chromosomes are called
autosomes
The cone-shaped base of an axon is called the
axon hillock
The summed effect of EPSPs and IPSPs determines whether an
axon hillock will reach threshold and generate an action potential
The speed of an action potential increases with the
axon's diameter
More complex animals have nerves, in which the
axons of multiple neurons are bundled together
The mechanisms of termination are different in
bacteria and eukaryotes
Antimicrobial proteins such as lysozyme break down
bacterial cell walls
Such viruses, called ___ (or ___), are widely used in molecular genetics research
bacteriophages; phages
Innate immunity includes
barrier defenses
Innate defenses of mammals include
barrier defenses phagocytosis antimicrobial peptides
Determination irreversibly commits a cell to
becoming a particular cell type
Morgan showed that Mendelian inheritance has its physical basis in the
behavior of chromosomes: scientific inquiry
If abnormal cells remain only at the original site, the lump is called a
benign tumor
Because prokaryotes evolved before eukaryotes, mitosis probably evolved from
binary fission
Prokaryotes (bacteria and archaea) reproduce by a type of cell division called
binary fission
In infected cells, MHC molecules
bind and transport antigen fragments to the cell surface, a process called antigen presentation
immunoglobulins
bind with specific antigens in the antigen-antibody response antibodies
In transduction, the
binding of the signaling molecule alters the receptor and initiates a signal transduction pathway
The repressor prevents gene transcription by
binding to the operator and blocking RNA polymerase
This DNA program directs the development of
biochemical, anatomical, physiological, and (to some extent) behavioral traits
Translation is a complex process in terms of its
biochemistry and mechanics
An example of quorum sensing is the formation of a
biofilm
Sleep is also regulated by the
biological clock and regions of the forebrain that regulate intensity and duration
Cycles of sleep and wakefulness are examples of circadian rhythms, daily cycles of biological activity. Such rhythms rely on a
biological clock, a molecular mechanism that directs periodic gene expression and cellular activity
Antibodies may also bind to toxins in body fluids and prevent them from
body cells
Morgan crossed flies that differed in traits of
body color and wing size The first cross was a P generation cross to generate F1 dihybrid flies. The second was a testcross
Adaptive immunity defends against infection of
body fluids and body cells
In metabolic processes of cell respiration and photosynthesis, prosthetic groups such as heme and iron-sulfur complexes are encountered in components of the electron transport chain. What do they do?
both oxidize and reduce during electron transport
A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____.
both parents are heterozygous for both genes Such a result indicates that the genes assort independently and that, for each gene, the alleles exhibit a dominant/recessive relationship.
Consanguineous matings (i.e., between close relatives) increase the chance that
both parents of a child carry the same rare allele
The currently accepted model suggests that protein-mediated bending of the DNA brings the
bound activators into contact with a group of mediator proteins
The midbrain and part of the hindbrain form the
brainstem, which joins with the spinal cord at the base of the brain
Mendel discovered the basic principles of heredity by
breeding garden peas in carefully planned experiments
Many signal molecules trigger formation of
cAMP
Summarize regulation by the lac operon when glucose is absent and lactose is absent
cAMP levels are high because glucose levels are low and, thus, CAP is active and will bind to the DNA. however, the lac repressor is also bound to the operator (because allolactose is not present) and RNA polymerase does not bind to the promoter. Transcription does not occur.
The cholera bacterium, Vibrio cholerae, produces a toxin that modifies a G protein so that it is stuck in its active form. This protein continually makes
cAMP, causing intestinal cells to secrete large amounts of salt into the intestines. Water follows by osmosis, and an untreated person can soon die from loss of water and salt.
A signal relayed by a signal transduction pathway may trigger an increase in
calcium in the cytosol
Two types of second messengers play an important role in de-etiolation:
calcium ions (Ca2+) and cyclic GMP (cGMP)
MicroRNAs
can bind to complementary sequences on mRNA molecules either degrading the target mRNA or blocking its translation
The immune system can act as a defense against viruses that cause
cancer and cancer cells that harbor viruses In 2006, a vaccine was released that acts against human papillomavirus (HPV), a virus associated with cervical cancer
There is evidence of telomerase activity in
cancer cells, which may allow cancer cells to persist
Mutations that decrease protein products of tumor-suppressor genes may contribute to
cancer onset
Recent advances in understanding the cell cycle and cell cycle signaling have led to advances in
cancer treatment
Oncogenes
cancer-causing genes in some types of viruses genes that cause cancer by blocking the normal controls on cell reproduction
The shortening of telomeres might protect cells from
cancerous growth by limiting the number of cell divisions
Abnormal functioning of RTKs is associated with many types of
cancers
In each of the three key phases of the Calvin cycle (carbon fixation, reduction, and regeneration),
carbon skeletons are modified in reactions that lead to the final products
Materials in the egg set up a program of gene regulation that is
carried out as cells divide
When the death signal is received, an apoptosis-inhibiting protein (Ced-9) is inactivated, triggering a cascade of
caspase proteins that promote apoptosis
Inducible enzymes usually function in
catabolic pathways (degenerative) , their synthesis is induced by chemical signal
Ribozymes
catalytic RNA molecules that function as enzymes and can splice RNA
DNA polymerases
catalyze the synthesis of new DNA at a replication fork
Enzymes called DNA polymerases
catalyze the elongation of new DNA at a replication fork
What is the function of reverse transcriptase?
catalyzing the formation of DNA from a RNA template
About 30 proteins make up the complement system, which
causes lysis of invading cells and helps trigger inflammation
Most of a neuron's organelles are in the
cell body (soma)
Cell division is an integral part of the
cell cycle
Cancer results from genetic changes that affect
cell cycle control
The sequential events of the cell cycle are directed by a distinct
cell cycle control system, which is similar to a clock
Signaling pathways can also affect the overall behavior of a cell; for example, a signal could lead to
cell division
The transformation from zygote to adult results from
cell division, cell differentiation, and morphogenesis
Lipid-soluble hormones diffuse across
cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells
A potato's response to light is an example of
cell signal processing
Inactivation mechanisms are an essential aspect of
cell signaling
The interaction of proteins is a major theme of
cell signaling Indeed, protein interaction is a unifying theme of all regulation at the cellular level. Many of the relay molecules in signal transduction pathways are protein kinases, and they often act on other protein kinases in the pathway.
A program of differential gene expression leads to the different
cell types in a multicellular organism
G protein-coupled receptors (GPCRs) are the largest family of
cell-surface receptors
G protein-coupled receptors (GPCRs) are
cell-surface transmembrane receptors that work with the help of a G protein
Cell differentiation is the process by which
cells become specialized in structure and function
The ability to catalyze compounds like lactose enables
cells deprived of glucose to survive
Binding of a B cell antigen receptor to an antigen is an early step in B cell activation. This gives rise to
cells that secrete antibodies (aka immunoglobulins (Ig))
An aster (a radial array of short microtubules) extends from each
centrosome
In animal cells, assembly of spindle microtubules begins in the
centrosome, the microtubule-organizing center
Bilaterally symmetrical animals (such as humans) exhibit
cephalization, the clustering of sensory organs at the front end of the body
The outer layer of the cerebrum is called the
cerebral cortex and is vital for perception, voluntary movement, and learning
telencephalon
cerebrum
The telencephalon develops into
cerebrum (includes cerebral cortex, basal nuclei)
Growth factors are released by
certain cells and stimulate other cells to divide
Nonsense mutations
change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein
Through antigenic variation, some pathogens are able to
change epitope expression and prevent recognition
The response to a lipid-soluble hormone is usually a
change in gene expression
Signals are detected by receptors, proteins that
change in shape in response to specific stimuli
Sex reversal
change sex for increased mating success -Bluehead wrasse (reef fish)
Point mutations
changes in a single nucleotide pair of a gene
An action potential results from
changes in membrane potential as ions move through voltage-gated channels
Graded potentials are
changes in polarization where the magnitude of the change varies with the strength of the stimulus
Mutations are
changes in the genetic information of a cell
Mutations
changes in the genetic material
leak channels
channels that are always open and allow ions to move along their gradient
Plasmodesmata
channels through cell walls that connect the cytoplasms of adjacent cells
A heritable feature that varies among individuals (such as flower color) is called a
character
G2 checkpoint
checks for cell size, DNA damage and DNA replication
G1 checkpoint
checks for cell size, nutrients, growth factors and DNA damage -Decision checkpoint - to divide or not to divide -Must pass this checkpoint for mitosis to begin
neurotransmitters
chemical messengers that cross the synaptic gaps between neurons
At chemical synapses, a
chemical neurotransmitter carries information between neurons
The opening of ion channels in the plasma membrane converts
chemical potential to electrical potential
Chemical modifications to histones and DNA of chromatin influence both
chromatin structure and gene expression
Eukaryotic chromosomes consist of
chromatin, a complex of DNA and protein that condenses during cell division
The genetic findings of Mendel and Morgan relate to the
chromosomal basis of recombination
In meiosis, cohesins are cleaved along the
chromosome arms in anaphase I (separation of homologs) and at the centromeres in anaphase II (separation of sister chromatids)
Biologists began to see parallels between the behavior of Mendel's proposed hereditary factors and chromosomes. Around 1902, Sutton and Boveri and others independently noted these parallels between and began to develop the
chromosome theory of inheritance
Biologists began to see parallels between the behavior of Mendel's proposed hereditary factors and
chromosomes
Most DNA is packaged into
chromosomes
Once separate, the chromatids are called
chromosomes
In late prophase II
chromosomes (each still composed of two chromatids) move toward the metaphase plate
inositol triphosphate (IP3) and diacylglycerol (DAG) are produced by
cleavage of a certain phospholipid in the plasma membrane
Chromosomes duplicate before meiosis. The resulting sister chromatids are
closely associated along their lengths This is called sister chromatid cohesion
The first response to broken skin is the release of
clotting proteins from platelets in the bloodstream, which decreases bleeding and helps to seal the wound.
Follicles
clusters of cells surrounding a single egg contain oocyte (egg); release 1/month; produce estrogens
Elongation occurs in three steps:
codon recognition, peptide bond formation, translocation
During its synthesis, a polypeptide chain begins to
coil and fold spontaneously into a specific shape—a three-dimensional molecule with secondary and tertiary structure
Different kinds of cells have different
collections of proteins
A diet high in fat increases the risk of both
colon and breast cancer
In polygenic inheritance
combined effect of two or more genes on a single character multiple genes independently affect a single trait
Local signaling in plants is not well understood beyond
communication between plasmodesmata
The RNA is ___ to the DNA template strand
complementary
The anticodon (on tRNA) base-pairs with
complementary codon in mRNA
If a cell receives a go-ahead signal at the G1 checkpoint, it will usually
complete the S, G2, and M phases and divide
However, the basic principles of segregation and independent assortment apply even to more
complex patterns of inheritance
In apoptosis,
components of the cell are chopped up and packaged into vesicles that are digested by scavenger cells
The hypothalamus constitutes a
control center that includes the body's thermostat and central biological clock
In eukaryotes, high levels of transcription of particular genes depend on
control elements interacting with specific transcription factors
Proximal control elements
control elements located close to the promoter
Associated with most eukaryotic genes are multiple
control elements, segments of noncoding DNA that serve as binding sites for transcription factors that help regulate transcription
Noncoding RNAs play multiple roles in
controlling gene expression
gene expression
conversion of the information encoded in a gene first into messenger RNA and then to a protein process by which a gene produces its product and the product carries out its function
Proto-oncogenes are the
corresponding normal cellular genes that are responsible for normal cell growth and division
Through summation, an IPSP can
counter the effect of an EPSP
Testcross
cross between an organism with an unknown genotype and an organism with a recessive phenotype
The accumulation of free oxygen in Earth's atmosphere began with the origin of
cyanobacteria that had both photosystem I and photosystem II.
When glucose (a preferred food source of E. coli) is scarce, CRP is activated by binding with
cyclic AMP (cAMP)
common second messengers
cyclic AMP and calcium ions
Some operons are also subject to positive control through a stimulatory protein, such as
cyclic AMP receptor protein (CRP), an activator of transcription
Two types of regulatory proteins are involved in cell cycle control:
cyclins and cyclin-dependent kinases (Cdks)
Antigen receptors on the surface of helper T cells bind to the antigen and the class II MHC molecule; then
cytokine signals are exchanged between the two cells
In plant cells, a cell plate forms during
cytokinesis
Cytokinesis separates the
cytoplasm
The response may occur in the
cytoplasm or nucleus
Intracellular receptor proteins are found in the
cytoplasm or nucleus of target cells
In female birds and frogs, estradiol, a form of estrogen, binds to a
cytoplasmic receptor in liver cells The estradiol-bound receptor activates transcription of genes needed to produce egg yolk
Cell-mediated response:
cytotoxic cells defend against infection in body cells
Suppression of the cell cycle can be important in the case of
damage to a cell's DNA
After exposure to light, a potato undergoes changes called ___, in which shoots and roots grow normally
de-etiolation
Graded potentials induce a small electrical current that leaks out of the neuron as it flows along the membrane. Graded potentials thus
decay with distance from their source. Although graded potentials are not the nerve signals that travel along axons, they have a major effect on the generation of nerve signals."
Edward B. Lewis, Christiane Nüsslein-Volhard, and Eric Wieschaus won a Nobel Prize in 1995 for
decoding pattern formation in Drosophila
Mendel's quantitative approach allowed him to
deduce principles that had remained elusive to others
The cystic fibrosis allele results in
defective or absent chloride transport channels in plasma membranes, leading to a buildup of chloride ions outside the cell Symptoms include mucus buildup in some internal organs and abnormal absorption of nutrients in the small intestine
The miRNAs and associated proteins cause
degradation of the target mRNA or sometimes block its translation
Most neurons have ___, highly branched extensions that receive signals from other neurons
dendrites
Excitatory postsynaptic potentials (EPSPs) are
depolarizations that bring the membrane potential toward threshold due to sodium influx through chemically-gated channels
Innate immune cells in mammals
detect, devour, and destroy invading pathogens
In reception, the target cell
detects a signaling molecule that binds to a receptor protein on the cell surface
Apoptosis evolved early in animal evolution and is essential for the
development and maintenance of all animals
Organogenesis:
development of 3 germ layers into organs
Morgan's discovery of a trait that correlated with the sex of flies was key to the
development of the chromosome theory of inheritance
internal development
development of the embryo within the body of the female High parental care Eg. placentals, sharks, some reptiles
A gene on the Y chromosome called SRY is responsible for
development of the testes in an embryo
Combining anatomical, genetic, and biochemical approaches, researchers have discovered
developmental principles common to many other species, including humans
Active immunity
develops naturally when a pathogen invades the body and elicits a primary or secondary immune response
Variation is demonstrated by the
differences in appearance that offspring show from parents and siblings
During embryonic development, a fertilized egg gives rise to many
different cell types
As the zygote divides by mitosis, cells contain
different cytoplasmic determinants, which lead to different gene expression
The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?
different possible assortment of chromosomes into gametes
Cones respond to
different wavelengths of light
Differences between cell types result from
differential gene expression, the expression of different genes by cells with the same genome
Interactions between cells induce
differentiation of specialized cell types
A cross between an individual with orange eyes and green skin and an individual with black eyes and white skin is an example of a _____ cross.
dihybrid The cross is examining two characters.
Mendel's second law was identified while studying two characters via a
dihybrid cross (a cross between F1 dihybrids, which can determine whether two characters are transmitted to offspring as a package or indepdently).
Crossing two true-breeding parents differing in two characters produces
dihybrids in the F1 generation, heterozygous for both characters
Meiosis produces haploid gametes from a
diploid parental cell.
Meiosis reduces the number of chromosome sets from
diploid to haploid
In local signaling, animal cells may communicate by
direct contact
Animal and plant cells have cell junctions that
directly connect the cytoplasm of adjacent cells
RNAi is used in the laboratory as a means of
disabling genes to investigate their function
Insertions and deletions have a
disastrous effect on the resulting protein more often than substitutions do
Pathogens
disease causing agents
Abnormalities in gene expression can lead to
diseases including cancer
antimicrobial peptides
disrupt pathogen plasma membranes
The same small set of cell-signaling mechanisms shows up in
diverse species and processes
About one in 1,000 males is XYY; these males
do not exhibit any syndrome
In many cases, different exons code for the different ___ in a protein
domains
One baby out of 400 in the United States is born with extra fingers or toes. This condition, polydactyly, is caused by a
dominant allele, found much less frequently in the population than the recessive allele
Some human disorders are caused by
dominant alleles
Mendel called the purple flower color a ___ ___ and the white flower color a ___ ___
dominant trait; recessive trait
"Provirus" is the name given to
double-stranded viral DNA that has been incorporated into a host cell's genome.
A single neurotransmitter may bind specifically to more than a
dozen different receptors
In contrast, exocrine glands, such as salivary glands, have
ducts to carry secreted substances onto body surfaces or into body cavities
Chromosomes ___ before meiosis
duplicate
At the end of anaphase
duplicate groups of chromosomes have arrived at opposite ends of the elongated parent cell
Late Interphase
duplicated chromosomes are in the relaxed uncondensed state; duplicated centrioles remain clustered
In 1882, the German anatomist Walther Flemming developed
dyes to observe chromosomes during mitosis and cytokinesis
In a cell in which DNA synthesis has occurred,
each chromosome is replicated
In the beginning of telophase I
each half of the cell has a haploid set of chromosomes; each chromosome still consists of two sister chromatids
Replication proceeds in both directions from
each origin, until the entire molecule is copied
Toll-like receptors
each recognize a specific "danger" molecule AND are embedded in cellular membranes.
The hormone epinephrine causes opposite effects in two populations of target cells because
each set of target cells has different receptor-transduction mechanisms
dispersive model
each strand of both daughter molecules contains a mixture of old and newly synthesized DNA
The human influenza virus mutates rapidly, and new flu vaccines must be made
each year
Three Embryonic Germ Layers
ectoderm, endoderm, mesoderm -For AP Test, you should know at least 2 derivatives of each germ layer.
Egg lodged in oviduct =
ectopic (tubal) pregnancy
Once activated, a B or T cell undergoes multiple cell divisions (clonal selection) to produce a clone of identical cells. Some cells from the clone become
effector cells that act immediately against the antigen
Parthenogenesis in female Blacktip Shark:
egg fuses with a polar body
The path of an egg takes to become a baby
egg 🡪 oviduct (fallopian tube) 🡪 uterus (baby) 🡪 cervix 🡪 vagina
The karyotype of one species of primate has 48 chromosomes. In a particular female, cell division goes awry and she produces one of her eggs with an extra chromosome (25). The most probable source of this error would be a mistake in which of the following?
either anaphase I or II
Most imprinted genes are critical for
embryonic development
The gene regulation systems that go wrong during cancer are the very same systems involved in
embryonic development
Endocrine cells are often grouped in ductless organs called
endocrine glands, such as the thyroid and parathyroid glands and testes or ovaries
Hormonal signaling in animals is called
endocrine signaling
Chemical signaling by hormones is the function of the
endocrine system
Negative feedback and antagonistic hormone pairs are common features of the
endocrine system
To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
endonuclease, DNA polymerase I, DNA ligase
G proteins bind the
energy-rich GTP
Macrophages are leukocytes that can
engulf and digest a pathogen.
Evolution of sexual reproduction
enhanced the ability of organisms to adapt to changing environments Advantage - Genetic diversity First involved exchange of genetic material between two cells and later led to sex cell formation
The other major source of developmental information is the
environment around the cell, especially signals from nearby embryonic cells
Another departure from Mendelian genetics arises when the phenotype for a character depends on
environment as well as genotype
The neurotransmitter molecules are cleared from the synaptic cleft via
enzyme degradation
separase
enzyme that degrades cohesin
Cortical reaction
enzymes prevent any other sperm from binding to the egg
The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence is called
epigenetic inheritance
The small, accessible part of an antigen that binds to an antigen receptor is called an
epitope
antigenic determinant
epitope
Most antigens recognized by B cells contain multiple
epitopes
Similarly, it was necessary for Engelmann to assume that the distribution of chloroplasts among the cells in the algal filament was approximately
equal. Fewer chloroplasts in one cell compared to another would mean a lower potential for oxygen production at any color. Engelmann's microscope was sufficiently powerful to see that Cladophora cells contain many small chloroplasts that were nearly uniform in their distribution within and between cells.
Telomeres postpone the
erosion of genes near the ends of DNA molecules
Sleep is
essential for survival and may play a role in the consolidation of learning and memory
Female reproductive system main hormone?
estrogens
Genetic variation produced in sexual life cycles contributes to
evolution
Crossing over contributes significantly to the genetic variation seen in gametes. This is because the
exchange of maternal and paternal genes between the nonsister chromatids of a homologous chromosome pair creates recombinant chromosomes with unique combinations of alleles. However, crossing over is not the only process that introduces genetic variation in meiosis I. The independent assortment of homologous chromosomes (which are never identical) in meiosis I produces daughter cells that differ from each other.
A single neurotransmitter could
excite postsynaptic cells expressing one receptor and inhibit postsynaptic cells expressing a different receptor
Water-soluble hormones are secreted by
exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors
Alternative RNA splicing can significantly
expand the repertoire of a eukaryotic genome
The cell cycle appears to be driven by specific chemical signals present in the cytoplasm. Some evidence for this hypothesis comes from
experiments in which cultured mammalian cells at different phases of the cell cycle were fused to form a single cell with two nuclei
DNA can be damaged by
exposure to harmful chemical or physical agents such as cigarette smoke and X-rays; it can also undergo spontaneous changes
exons
expressed sequence of DNA; codes for a protein usually translated into amino acid sequences
In genomic imprinting, methylation regulates
expression of either the maternal or paternal alleles of certain genes at the start of development
Klinefelter syndrome is the result of an
extra chromosome in a male, producing XXY individuals
A pedigree is a
family tree that describes the interrelationships of parents and children across generations Inheritance patterns of particular traits can be traced and described using pedigrees
Local regulators such as the prostaglandins are modified
fatty acids
A cell can regulate the production of enzymes by
feedback inhibition or by gene regulation
A person with two X chromosomes develops as a
female
In one experiment, Morgan mated male flies with white eyes (mutant) with
female flies with red eyes (wild type). -The F1 generation all had red eyes -The F2 generation showed a 3:1 red to white eye ratio, but only males had white eyes
Translation initiation factors are simultaneously activated in an egg following
fertilization
Aneuploidy results from the
fertilization of gametes in which nondisjunction occurred
If the concentration of external signaling molecules falls,
fewer receptors will be bound
Such regulatory mechanisms allow a cell to
fine-tune gene expression rapidly in response to environmental changes
F1
first filial generation; The hybrid offspring of the P generation
In vertebrates, innate immunity is a
first response to infections and the foundation of adaptive immunity
The binding of a signaling molecule to a receptor triggers the
first step in a chain of molecular interactions
external development
fish & amphibians have external fertilization in water; reptiles, birds, and some mammals (e.g. monotremes) have internal fertilization then lay eggs. No placenta. Tough eggshell Eg. reptiles, birds, platypus
B cells can express ___ different forms (or classes) of immunoglobulin (Ig) with similar antigen-binding specificity but different heavy chain C regions
five
Mendel reasoned that only the purple flower factor was affecting
flower color in the F1 hybrids
FSH
follicle-stimulating hormone
During embryonic development, the anterior neural tube gives rise to the
forebrain, midbrain, and hindbrain
The vertebrate brain has three major regions:
forebrain, midbrain, hindbrain
A type of T cell called a helper T cell activates both the humoral and cell-mediated immune responses. This requires the presence of a
foreign molecule that can bind the antigen receptor on the helper T cell And the antigen must be displayed on the surface of an antigen-presenting cell
The neuron is a cell that exemplifies the close fit between
form and function
Myoblasts are cells determined to
form muscle cells and produce large amounts of muscle-specific proteins
The fornix, as well as the hippocampus and amygdala, play a role in the
forming of new and short-term memories.
A promoter called a TATA box is crucial in
forming the initiation complex in eukaryotes
diencephelon
forms endocrine tissues in the brain An important structure adjacent to the brainstem that contains the hypothalamus (which controls emotions) and the thalamus (which relays sensory impulses to various portions of the cerebral cortex) is called the:
Consider pea plants with the genotypes GgTt and ggtt . These plants can each produce how many type(s) of gametes?
four ... one GgTt individuals can produce the following gametes: GT, Gt, gT, and gt. A ggtt plant can produce only gt.
At the end of meiosis, there are
four daughter cells, each with a haploid set of unreplicated chromosomes Each daughter cell is genetically distinct from the others and from the parent cell
The two cell divisions of meiosis result in
four daughter cells, rather than the two daughter cells in mitosis
Spermatogenesis produces
four haploid cells
Cytotoxic T cells recognize
fragments of foreign proteins produced by infected cells
DNA polymerases add nucleotides only to the
free 3′ end of a growing strand; 3' end of the strand, never to the 5' end.
Pattern formation has been extensively studied in the
fruit fly Drosophila melanogaster
The nervous and endocrine systems often overlap in
function
Neuron structure and organization reflect
function in information transfer
T cell and B cell antigen receptors are
functionally different
GPCR systems are extremely widespread and diverse in their
functions
Sexual reproduction involves
fusion of halpoid gametes Egg (ovum) + Sperm = Zygote
Pedigrees can also be used to make predictions about
future offsrping
When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.
gametes, progeny
For example, depolarization occurs if
gated Na+ channels open and Na+ diffuses into the cell
What Mendel called a "heritable factor" is what we now call a
gene
Some introns contain sequences that may regulate
gene expression
Prokaryotes and eukaryotes precisely regulate
gene expression in response to environmental conditions
Sex-linked gene
gene located on the X or Y chromosome
Alterations of chromosome number or structure can cause some
genetic disorders
Mutations (changes in an organism's DNA) are the original source of
genetic diversity
Sexual reproduction advantage
genetic diversity; ability to change population when environment changes
Alfred Sturtevant, one of Morgan's students, constructed a
genetic map, an ordered list of the genetic loci along a particular chromosome
The "blending" hypothesis is the idea that
genetic material from the two parents blends together (like blue and yellow paint blend to make green)
Reshuffling of alleles during sexual reproduction produces
genetic variation
Crossing over contributes to
genetic variation by combining DNA from two parents into a single chromosome
A clone is a group of
genetically identical individuals from the same parent
Halobacterium has a photosynthetic membrane that appears purple. Its photosynthetic action spectrum is the inverse of the action spectrum for green plants. (That is, the Halobacterium action spectrum has a peak where the green plant action spectrum has a trough.) What wavelengths of light do the Halobacterium photosynthetic pigments absorb?
green and yellow
anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
Distal control elements,
groupings of which are called enhancers, may be far away from a gene or even located in an intron
Platelet-derived growth factor
growth factor for endothelium, smooth muscle and fibroblasts
The low pH of skin and the digestive system prevents
growth of many bacteria
The two cell divisions of meiosis result in four daughter cells, rather than the two daughter cells in mitosis. Each daughter cell has only
half as many chromosomes as the parent cell
Gametes (reproductive cells: sperm and eggs) have
half as many chromosomes as somatic cells
If one chromosome undergoes nondisjunction in meiosis II
half the gametes will have the normal haploid number of chromosomes (n), one-quarter will have an extra chromosome (n +1), and one-quarter will be missing a chromosome (n - 1).
If all chromosomes undergo nondisjunction in meiosis II
half the gametes will have the normal haploid number of chromosomes (n), one-quarter will have twice the haploid number (2n), and one-quarter will have no chromosomes.
If all chromosome pairs undergo nondisjunction in meiosis I
half the gametes will have twice the normal haploid number of chromosomes (2n), and half will have no chromosomes.
Once meiosis I is completed, cells are
haploid
At sexual maturity, the ovaries and testes produce
haploid gametes
Unlike graded potentials, action potentials
have a constant magnitude and can regenerate in adjacent regions of the membrane. Action potentials can therefore spread along axons, making them well suited for transmitting a signal over long distances.
Silent mutations
have no effect on the amino acid produced by a codon because of redundancy in the genetic code
In light repair
he covalent bonds between the thymine dimers are broken In light repair, visible light provides the energy to cleave the bonds between the thymines.
For Engelmann to be able to draw meaningful conclusions from his experiment, he had to assume that
he number of bacteria at any location on the slide was proportional to the amount of oxygen produced by the alga at that location. If this were not the case, the distribution of the bacteria around the alga would be of no use in determining the amount of photosynthesis that occurs at each wavelength.
Transcription steps
helicase and topsisomerase unwind DNA double helix RNA polymerase II binds to TATA box within promoter region of gene hnRNA synthesized from DNA template strand 1. Initiation 2. Elongation 3. Termination
Human immunodeficiency virus (HIV) infects
helper T cells
Activation of B cells involves
helper T cells and proteins on the surface of pathogens
Hemocytes (the *WBCs* of the invertebrate) circulate within ___ (similar to blood) and
hemolymph; carry out phagocytosis, the ingestion and digestion of foreign substances including bacteria
An organism with two different alleles for a gene is a ___ and is said to be ___ for the gene controlling that character
heterozygote; heterozygous
In a testcross, if any offspring display the recessive phenotype, the mystery parent must be
heterozygous
Carriers are
heterozygous individuals who carry the recessive allele but are phenotypically normal
HIV persists in the host—despite an immune response—because it has a
high mutation rate that promotes antigen variation
Localized tumors may be treated with
high-energy radiation, which damages the DNA in the cancer cells
Neurons are
highly specialized cells that receive and transmit information from one area of the body to another.
Mendel documented a particulate mechanism through
his experiments with garden peas
P site
holds the tRNA carrying the growing polypeptide chain
A site (ribosome)
holds the tRNA carrying the next amino acid to be added to the chain
blastula
hollow ball of cells
Endocrine signaling maintains
homeostasis, mediates responses to stimuli, regulates growth and development
Edward B. Lewis discovered
homeotic genes, which control pattern formation in the late embryo, larva, and adult stages
Human females have a
homologous pair of X chromosomes (XX)
An organism with two identical alleles for a character is called a
homozygote It is said to be homozygous for the gene controlling that character
Feedback regulation and coordination with the nervous system are common in
hormone pathways
In long-distance signaling, plants and animals use chemicals called
hormones
Antagonistic hormones
hormones that have opposing physiological properties, but that work together. Ex. insulin & glucagon have opposite effects on blood sugar levels.
major histocompatibility complex (MHC) molecules
host cell surface proteins that present antigen to T cells
Some pathogens have evolved ways to diminish the effectiveness of
host immune responses
Many body fluids including saliva, mucus, and tears are ___ to many microbes
hostile
Communication among microorganisms provides some insight into
how cells send, receive, and respond to signals
Earl W. Sutherland and colleagues discovered
how the hormone epinephrine acts on cells
Human viruses occasionally exchange genes with the viruses of domesticated animals. This poses a danger, as
human immune systems are unable to recognize the new viral strain
The menstrual cycle is seen in
humans and other primates
A type of T cell called a helper T cell activates both the
humoral and cell-mediated immune responses
The defenses provided by B and T lymphocytes can be divided into the
humoral immune response and the cell-mediated immune response
The cell body of a postsynaptic neuron may receive inputs from
hundreds or thousands of synaptic terminals
Inhibitory postsynaptic potentials (IPSPs) are
hyperpolarizations that move the membrane potential farther from threshold hyperpolarizations caused by cation exit or anion entry
Almost all the cells in an organism contain an
identical genome
Adrian Srb and Norman Horowitz
identified three classes of arginine-deficient mutants Each lacked a different enzyme necessary for synthesizing arginine. The results of the experiments provided support for the one gene-one enzyme hypothesis
Mismatch repair
identifies and corrects incorrectly matched nucleotides.
All animals have innate immunity, a defense active
immediately upon infection
Pathogens have evolved mechanisms to thwart
immune responses
Active immunity can develop following
immunization
The projection provided by a second immune response provided the basis for
immunization
DNA methylation can cause long-term
inactivation of genes in cellular differentiation
Unbound receptors revert to an
inactive state
Pathway branching and "cross-talk" further help the cell coordinate
incoming signals
When gated (not leak) K+ channels open, K+ diffuses out, making the inside of the cell more negative. This is hyperpolarization, an
increase in magnitude of the membrane potential
Consanguineous matings
increase the chance of mating between two carriers of the same rare allele
The site of inflammation may also become red due to
increased blood flow at the site
The site of inflammation may become swollen due to the
increased numbers of cells and fluids at the site and painful due to signals from pain receptors.
Three mechanisms contribute to genetic variation:
independent assortment of chromosomes, crossing over, random fertilization
The spinal cord also produces reflexes
independently of the brain
Recessively inherited disorders show up only in
individuals homozygous for the allele
A molecule called an ___ inactivates the repressor to turn the lac operon on
inducer
The lac operon is an
inducible operon and contains genes that code for enzymes used in the hydrolysis and metabolism of lactose
In the process called ___, signal molecules from embryonic cells cause changes in nearby target cells
induction
The timing of onset of a disease significantly affects its
inheritance
X-linked genes follow a specific pattern of
inheritance
Morgan did experiments with fruit flies to see how linkage affects
inheritance of two characters
Genes located near each other on the same chromosome tend to be
inherited together
Morgan found that body color and wing size are usually
inherited together in specific combinations (parental phenotypes) He noted that these genes do not assort independently and reasoned that they were on the same chromosome. Nonparental phenotypes were also produced in the testcross
Offspring acquire genes from parents by
inheriting chromosomes
Further regulation of cell metabolism is provided by G protein systems that
inhibit adenylyl cyclase
Tumor-suppressor genes normally
inhibit cell division
The nerve gas sarin triggers paralysis and death due to
inhibition of the enzyme that breaks down the neurotransmitter controlling skeletal muscles
Ced-9
inhibitor of Ced-4; inhibits apoptosis
Chromatin-modifying enzymes provide
initial control of gene expression by making a region of DNA either more or less able to bind the transcription machinery
Vertebrates have both ___ and ___ immunity
innate and adaptive
Interferon proteins provide
innate defense, interfering with viruses and helping activate macrophages
Endoderm
innermost germ layer; develops into the linings of the digestive tract and much of the respiratory system -Epithelial linings of digestive, respiratory, excretory tracts -Liver, pancreas
Pathways leading to the release of calcium involve ___ and ___ as additional second messengers
inositol triphosphate (IP3) and diacylglycerol (DAG)
The rate at which action potentials are produced in a neuron is proportional to
input signal strength
Which are more dangerous, insertions/deletions or substitutions?
insertions/deletions bc they alter reading frame
In most neurons, the concentration of K+ is higher ___ the cell, while the concentration of Na+ is higher ___ the cell
inside; outside
Induction:
interaction among cells that influences their fate, cause changes in gene expression
The simplest animals with nervous systems, the cnidarians, have
interconnected neurons arranged in nerve nets
Plasma cells develop from B cells that have been stimulated by the
interleukin-2 secreted by helper T cells.
Certain protists exhibit types of cell division that seem
intermediate between binary fission and mitosis ex: bacteria, diatoms and some yeasts, dinoflagellates, most eukaroyotes
The cell cycle control system is regulated by both
internal and external controls
Nucleoli are present during _____.
interphase
RNA interference (RNAi)
introduction of double-stranded RNA into a cell to inhibit gene expression
Internal signals can result from
irreparable DNA damage or excessive protein misfolding
In autocrine signaling, the target cell
is also the secreting cell
Tay-Sachs disease
is fatal; a dysfunctional enzyme causes an accumulation of lipids in the brain -At the organismal level, the allele is recessive -At the biochemical level, the phenotype (i.e., the enzyme activity level) is incompletely dominant -At the molecular level, the alleles are codominant
Now that the TKR receptor is fully activated
it is recognized by specific relay proteins inside the cell. Each such protein binds to a specific phosphorylated tyrosine, undergoing a resulting structural change that activates the bound protein. Each activated protein triggers a transduction pathway, leading to a cellular response."
Ca2+ can function as a second messenger because
its concentration in the cytosol is normally much lower than the concentration outside the cell
Positional information, the molecular cues that control pattern formation, tells a cell
its location relative to the body axes and to neighboring cells
A synapse is a
junction between an axon and another cell
Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?
lack of appropriate cell death
Albinism is a recessive condition characterized by a
lack of pigmentation in skin and hair
Scaffolding proteins are
large relay proteins to which other relay proteins are attached
When does the synaptonemal complex disappear?
late prophase of meiosis I
Some viruses may remain in a host in an inactive state called
latency ex: Herpes simplex viruses can be present in a human host without causing symptoms
Using a dihybrid cross, Mendel developed the
law of independent assortment
You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent
leading strands and Okazaki fragments.
Apoptosis prevents enzymes from
leaking out of a dying cell and damaging neighboring cells
An enzyme called telomerase catalyzes the
lengthening of telomeres in germ cells
In bacteria, the elongation cycle takes
less than a tenth of a second
Nervous system organization usually correlates with
lifestyle
Direct synaptic transmission involves binding of neurotransmitters to
ligand-gated ion channels in the postsynaptic cell
The reactions that produce molecular oxygen (O2) take place in the ___ ___ alone
light reactions
At first, Watson and Crick thought the bases paired
like with like (A with A, and so on), but such pairings did not result in a uniform width
Sturtevant used recombination frequencies to make
linkage maps of fruit fly genes
Genes that are located on the same chromosome tend to be inherited together and are called
linked genes
Steroid hormones and other largely nonpolar hormones are
lipid-soluble
In their mechanism of action, a difference between lipid-soluble and water-soluble hormones is that
lipid-soluble hormones bind to an intracellular receptor and this hormone-receptor complex binds to DNA
Nitric oxide (NO) is a gas that functions in the body as both a
local regulator and a neurotransmitter
Excision repair
locates and repairs incorrect sequence by removing a segment of the DNA and then adding the correct nucleotides
A gene's specific position along a chromosome is called its
locus
action potentials
long distance signals of axons
Most eukaryotic genes and their RNA transcripts have
long noncoding stretches of nucleotides that lie between coding regions
Immunological memory is responsible for
long-term protections against diseases
Red has a ___ wavelength than green.
longer
Acetylation of histone tails promotes
loose chromatin structure that permits transcription
The digestive system is protected by a chitin-based barrier and
lysozyme, an enzyme that breaks down bacterial cell walls
RNA processing converts the RNA transcript into _____.
mRNA
Template of Translation
mRNA
Product Synthesized in Transcription
mRNA molecule
The initiation stage of translation brings together
mRNA, a tRNA with the first amino acid, and the two ribosomal subunits
Fertilization and meiosis alternate in sexual life cycles to
maintain chromosome number
T cells bind to antigen fragments displayed or presented on a host cell. These antigen fragments are bound to cell-surface proteins called
major histocompatibility complex (MHC) molecules
Researchers are uncovering more evidence of biological roles for these ncRNAs every day. This represents a
major shift in the thinking of biologists
Polyribosomes enable a cell to
make many copies of a polypeptide very quickly
X-linked recessive disorders are much more common in
males than in females
X chromosomes have genes for
many characters unrelated to sex
A neuron at resting potential contains
many open K+ channels (these are called leak channels - they are always open) and fewer open Na+ channels; K+ diffuses out of the cell
The hormone epinephrine (or adrenaline) regulates
many organs in response to stressful situations
Pheromones serve many functions, including
marking trails leading to food, defining territories, warning of predators, and attracting potential mates
The leukocytes of the innate immune system are
mast cells, macrophages, and neutrophils
In the lymph nodes, an antigen is exposed to a steady stream of lymphocytes until a
match is made
Cytoplasmic determinants are
maternal substances in the egg that influence early development unevenly distributed cytoplasmic components of an unfertilized egg, often involved in transcriptional regulation, usually separated in the first few mitotic divisions following fertilization, and maternal contributions that help to direct the initial stages of development.
Transcription factors
mediate the binding of RNA polymerase and the initiation of transcription
The myelencephalon develops into
medulla oblongata
Gametes are produced by a variation of cell division called
meiosis
Meiosis takes place in two consecutive cell divisions, called
meiosis I and meiosis II
DNA content is halved in both
meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II.
Gametes are the only types of human cells produced by
meiosis, rather than mitosis
Every cell has a voltage (difference in electrical charge) across its plasma membrane called a
membrane potential
Intracellular recording can be used to monitor the changes in
membrane potential
The resulting buildup of negative charge within the neuron is the major source of
membrane potential
Receptor tyrosine kinases (RTKs) are
membrane receptors that transfer phosphate groups from ATP to another protein
In the secondary immune response
memory cells facilitate a faster, more efficient response from a reservoir of T and B memory cells
The remaining cells in the clone become long-lived
memory cells that can give rise to effector cells if the same antigen is encountered again
Midbrain
mesencephalon
Transcription produces
messenger RNA (mRNA)
In mitosis, cohesins are cleaved at the end of
metaphase
During which phase does independent assortment occur?
metaphase I
Understanding of the role of cAMP in G protein signaling pathways helps explain how certain
microbes cause disease
The brainstem consists of the
midbrain, pons, medulla
Many genetic disorders are inherited in a recessive manner. These range from relatively
mild to life-threatening
By combining variable elements, the immune system assembles
millions of different antigen receptors from a small number of parts
The zygote produces somatic cells by
mitosis and develops into an adult
The cell cycle consists of
mitotic (M) phase (mitosis and cytokinesis) and interphase (cell growth and copying of chromosomes in preparation for cell division)
The eukaryotic cell cycle is regulated by a
molecular control system
This phosphorylation and dephosphorylation system acts as a
molecular switch, turning activities on and off or up or down, as required
The inflammatory response, such as pain and swelling, is brought about by
molecules released upon injury or infection
Local regulators are
molecules that are secreted by a signaling cell. These regulators may travel short distances and influence cells in the vicinity. One class of local regulators in animals is growth factors, which are compounds that stimulate nearby cells to grow and divide.
Macrophages are WBCs derived from
monocytes.
Mendel's first law was identified while studying one character via a
monohybrid cross (a cross between heterozygotes that are heterozygous for one character).
Mendel derived the law of segregation by following a single character. The F1 offspring produced in this cross were
monohybrids, heterozygous for one character
Dominant alleles are not necessarily ___ common in populations than recessive alleles
more
The physical processes that give an organism its shape constitute
morphogenesis
The behavior of chromosomes during meiosis and fertilization is responsible for
most of the variation that arises in each generation
As the spindle depolymerizes, the kinetochores appear to
move along the spindle fiber, dragging the attached chromosomes with them.
In a tautomeric shift, hydrogen atoms
move to form a base with altered hydrogen properties
The cerebellum coordinates
movement and balance and helps in learning and remembering motor skills
Translocation
moves a segment from one chromosome to another
Traits that depend on multiple genes combined with environmental influences are called
multifactorial
Once activated, a B or T cell undergoes
multiple cell divisions (clonal selection) to produce a clone of identical cells
Apoptosis integrates
multiple cell-signaling pathways
Probability in an F1 monohybrid cross can be determined using the
multiplication rule
Cell signaling is usually a ___ process
multistep
Myoblasts produce
muscle specific proteins and form skeletal muscle cells
Acetylcholine is involved in
muscle stimulation, memory formation, and learning
frameshift mutation
mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide
Cancer can be caused by
mutations to genes that regulate cell growth and division
embryonic lethals
mutations with phenotypes causing death at the embryonic or larval stage
In vertebrates, axons are insulated by a
myelin sheath, which causes an action potential's speed to increase
Cellular innate defenses in vertebrates also involve
natural killer cells
Nonspecific defense includes
natural killer cells that destroy virus-infected body cells, and abnormal cells that could form tumors.
This abundance of genetic variation is the raw material upon which
natural selection works
In paracrine signaling, the target cells lie
near the secreting cells
Regulation of both the trp and lac operons involves
negative control of genes because operons are switched off by the active form of the repressor
For hormones that homeostatically regulate cellular functions,
negative feedback typically regulates hormone secretion.
Mutations in genes that encode ion channels lead to disorders affecting the
nerves or brain—or the muscles or heart
Gated ion channels and action potentials play an important role in
nervous system activity
Which category of signal exerts its effects on target cells by binding to membrane-bound receptor proteins?
neurohormones
Neuroendocrine signaling
neurohormones diffuse into the bloodstream and trigger responses in target cells anywhere in the body
In neuroendocrine signaling, specialized neurosecretory cells secrete
neurohormones that diffuse from nerve endings into the bloodstream
Nervous systems consist of circuits of
neurons and supporting cells
Changes in membrane potential occur because
neurons contain gated ion channels that open or close in response to stimuli
Interneurons
neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs integrate (analyze and interpret) the information
The action potential causes the release of the
neurotransmitter
The presynaptic neuron synthesizes and packages the
neurotransmitter in synaptic vesicles located in the synaptic terminal
At synapses, secreted molecules called ___ diffuse short distances and bind to receptors on target cells
neurotransmitters
What is contained within the synaptic vesicles?
neurotransmitters
Recombinant chromosomes bring alleles together in
new combinations in gametes
nonparental phenotypes
new combinations of traits
DNA polymerases proofread
newly made DNA, replacing any incorrect nucleotides
When voltage-gated ion channels close
no ions flow across membrane.
Because of crossing over in meiosis I, the two sister chromatids of each chromosome are
no longer genetically identical
Voltage-gated sodium channels are restricted to
nodes of Ranvier, gaps in the myelin sheath
A significant fraction of the genome may be transcribed into
noncoding RNAs (ncRNAs)
If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?
none Alleles of the same gene must separate during gamete formation; thus, the two B alleles would be distributed to different gametes.
Meiosis yields
nonidentical daughter cells that have only one set of chromosomes, half as many as the parent cell
The ability of organisms to produce more of their own kind best distinguishes living things from
nonliving matter
Morgan observed that although some genes are linked,
nonparental allele combinations are still produced
Crossing over occurs only between
nonsister chromatids within a homologous pair of chromosomes, not between the sister chromatids of a replicated chromosome. Only segments near the ends of the chromatids, not segments nearest the centromeres, can exchange DNA.
Co-expressed eukaryotic genes
not organized in operons, can be scattered over different chromosomes, but each has the same combination of control elements
Some scientists considered whether these types of (single) mutations could contribute to evolution by generating
novel body shapes This line of inquiry gave rise to the field of evolutionary developmental biology, "evo-devo"
In eukaryotes, the ___ ___ separates the processes of transcription and translation.
nuclear envelope; RNA undergoes processing before leaving the nucleus
What process repairs damage to a preexisting double helix?
nucleotide excision repair In nucleotide excision repair, a section of DNA containing the damage is removed, and the gap is then filled in and completed by DNA polymerase and DNA ligase.
DNA is a polymer of
nucleotides
Location of Transcription in Eukaryotic Cells
nucleus
Mitosis conserves the
number of chromosome sets, producing cells that are genetically identical to the parent cell
Meiosis reduces the
number of chromosomes sets from two (diploid) to one (haploid), producing cells that differ genetically from each other and from the parent cell
The alleles of one gene segregate into gametes independently
of another gene's alleles
A response to a signal may not be simply
on or off
An activated hormone-receptor complex can act as a transcription factor, turning
on or off specific genes
A male develops from a zygote with
one X and one Y
Human males have
one X and one Y chromosome
Each pair of homologous chromosomes includes
one chromosome from each parent
A monosomic zygote has only
one copy of a particular chromosome
Action potentials travel in only
one direction: toward the synaptic terminals
The 46 chromosomes in a human somatic cell are two sets of 23:
one from the mother and one from the father
Oogenesis produces
one functional ovum and three nonfunctional polar bodies
As a result of nondisjunction
one gamete receives two of the same type of chromosome, and another gamete receives no copy
Many heritable characters are not determined by only
one gene with two alleles
Beadle and Tatum's hypothesis
one gene-one polypeptide hypothesis Many proteins are composed of several polypeptides, each of which has its own gene
cyclin
one of a family of closely related proteins that regulate the cell cycle in eukaryotic cells a protein that is called that because its concentration is clyclically fluctuating in the cell
MyoD
one of several "master regulatory genes" that produce proteins that commit the cell to becoming skeletal muscle; transcription factor that binds to enhancers of various target genes
Phosphate groups can't be attached to just any part of a protein. Instead, they are typically linked to
one of the three amino acids that have hydroxyl (-OH) groups in their side chains: tyrosine, threonine, and serine.
Cystic fibrosis is the most common lethal genetic disease in the United States, striking
one out of every 2,500 people of European descent
Griffith worked with two strains of a bacterium...
one pathogenic and one harmless
Activators have two domains,
one that binds DNA and a second that activates transcription
Vertebrates have two major classes of acetylcholine receptor:
one that is ligand gated and one that is metabotropic
An inducible operon is
one that is usually off; a molecule called an inducer inactivates the repressor and turns on transcription
In humans, an average of ___ crossover events occurs per chromosome
one to three
Each enhancer is generally associated with
only one gene and no other
Natural selection has favored bacteria that produce
only the gene products needed by that cell
Voltage-gated ion channels
open or close in response to a change in voltage across the plasma membrane of the neuron
One mechanism for control of gene expression in bacteria is the
operon model
Co-expressed eukaryotic genes are not organized in
operons (with a few exceptions)
The role of cytotoxic T cells is the secretion of _____, which plays a role in the _____ immune response.
perforin ... cell-mediated Perforin causes the lysis of pathogen-infected body cells; it is a component of the cell-mediated immune response.
B cells are not
phagocytic
Internal defenses:
phagocytic cells, natural killer cells, antimicrobial proteins, inflammatory response
In the example of flower color in pea plants, PP and Pp plants have the same
phenotype (purple) but different genotypes
After the signal molecule binds to the receptor and a dimer forms the tyrosine-kinase section is activated and
phosphate is added to the tyrosine from _an ATP molecule on the tail of another monomer
Reduction of NADP+ occurs during
photosynthesis
Mutagens
physical and chemical agents that interact with DNA to cause mutations
An organism's phenotype includes its
physical appearance, internal anatomy, physiology, and behavior
Genes that are far apart on the same chromosome can have a recombination frequency near 50%. Such genes are
physically linked, but genetically unlinked, and behave as if found on different chromosomes
Hormones are released from an endocrine cell, travel through the bloodstream, and interact with specific receptors within a target cell to cause a
physiological response
In de-etiolation, the receptor is a
phytochrome capable of detecting light
In binary fission, the plasma membrane
pinches inward, dividing the cell into two
Which of these cells produce and secrete antibodies?
plasma cells Plasma cells are clones of antibody-secreting B cells
A variety of B cells activated by one antigen will give rise to
plasma cells producing antibodies directed against different epitopes of the common antigen
Effector cells
plasma cells that secrete antibodies
Where are most signal receptors located?
plasma membrane
Most signal receptors are
plasma membrane proteins
natural killer cells
play an important role in the killing of cancer cells and cells infected by viruses These circulate through the body and detect abnormal cells They release chemicals leading to cell death, inhibiting the spread of virally infected or cancerous cells
Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?
pleiotropy
Most genes have multiple phenotypic effects, a property called
pleiotropy
Streptococcus pneumoniae is one such bacterium, a major cause of
pneumonia and meningitis in humans
The phenotypic range is broadest for
polygenic characters
Quantitative variation usually indicates
polygenic inheritance, an additive effect of two or more genes on a single phenotype
Often translation is not sufficient to make a functional protein so
polypeptide chains are modified after translation or targeted to specific sites in the cell
Many proteins are composed of several ___, each of which has its own gene
polypeptides
Product synthesized in translation
polypeptides
Hormones fall into three major classes:
polypeptides, steroids, amines
Local regulators such as the prostaglandins are modified fatty acids. Others are ___, and some are ___.
polypeptides; gases
Multiple ribosomes can translate a single mRNA simultaneously, forming a
polyribosome (or polysome)
The metencepahlon develops into
pons, cerebellum
locus
position of a gene on a chromosome
Watson and Crick noted that the specific base pairing suggested a
possible copying mechanism for genetic material
The attraction of opposite charges across the membrane is a source of
potential energy
For genes that are not expressed all the time, high levels of transcription depend on the
presence of another set of factors, specific transcription factors
Rods interpret the
presence/absence of light
When an antigen binds a B cell, the cell takes in a few foreign molecules by receptor-mediated endocytosis. The class II MHC protein of the B cell then
presents an antigen fragment to a helper T cell, a process that is critical to B cell activation
Information is transmitted from a
presynaptic cell (a neuron) to a postsynaptic cell (a neuron, muscle, or gland cell)
First lines of defense help
prevent pathogens from gaining entry to the body
Both the humoral and cell-mediated responses can include
primary and secondary immune responses
The first exposure to a specific antigen represents the
primary immune response
A gene determines
primary structure
RNA polymerase does not need a
primer
Most DNA polymerases require a
primer and a DNA template strand
DNA polymerases require a
primer to which they can add nucleotides
The multiplication rule states that the
probability that two or more independent events will occur together is the product of their individual probabilities
We can use the multiplication and addition rules to predict the
probability of specific phenotypes
The rule of addition can be used to figure out the
probability that an F2 plant from a monohybrid cross will be heterozygous rather than homozygous
Gene expression
process by which a gene produces its product and the product carries out its function
transformation
process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria a change in genotype and phenotype due to assimilation of foreign DNA
Male reproductive system function
produce and deliver sperm
Alpha cells of the pancreas
produce glucagon
Beta cells of the pancreas
produce insulin
neurohormones
produced and released by neurons in the brain, rather than by the endocrine glands, and delivered to organs and tissues through the bloodstream
Female reproductive system function
produces eggs for reproduction and provides place for growing baby.
An activated B cell gives rise to thousands of identical plasma cells. These begin
producing and secreting antibodies
The change of a single nucleotide in a DNA template strand can lead to the
production of an abnormal protein
Ancestral signaling molecules likely evolved in
prokaryotes and single-celled eukaryotes and were adopted for use in their multicellular descendants
An operator is usually positioned within the
promoter
Mitosis is conventionally broken down into five stages:
prophase prometaphase metaphase anaphase telophase
Synapsis, the pairing of homologous chromosomes, occurs during
prophase I
Local regulators that mediate paracrine and autocrine signaling include the
prostaglandins
This ubiquitin mark is recognized by
proteasomes, which recognize and degrade the proteins
Post-translational modifications may be required before the
protein can begin doing its particular job in the cell
Neurons are able to change their polarized state because they have
protein channels (that other cells don't have) within their membrane that can respond to stimuli
Kinetochores
protein complexes associated with centromeres
cAMP usually activates
protein kinase A, which phosphorylates various other proteins
Histones
protein molecules around which DNA is tightly coiled in chromatin
The receptor activates another protein, which activates another, and so on, until the
protein producing the response is activated
The operon can be switched off by a
protein repressor
Bound activators facilitate a sequence of
protein-protein interactions that result in transcription of a given gene
A small fraction of DNA codes for
proteins
What is the product of gene expression?
proteins
What type of molecule are most signal receptors?
proteins
interferons
proteins (cytokines) secreted by T cells and other cells to aid and regulate the immune response
The same signal can have different effects in cells with different
proteins and pathways
The two ribosomal subunits (large and small) are made of
proteins and ribosomal RNA (rRNA)
After interphase, the sister chromatids are held together by
proteins called cohesins
It is common to refer to gene products as
proteins rather than polypeptides
The activated cytotoxic T cell secretes
proteins that disrupt the membranes of target cells and trigger apoptosis
synaptonemal complex
proteins that hold together homologous chromosomes
Mendel's "hereditary factors" were
purely abstract when first proposed
Instead, pairing a ___ (A or G) with a ___ (C or T) resulted in a uniform width consistent with the X-ray data
purine; pyrimidine
The nitrogenous bases can be
purines or pyrimidines adenine (A), thymine (T), guanine (G), or cytosine (C)
Nonkinetochore microtubules from opposite poles overlap and
push against each other, elongating the cell
A concentration of signaling molecules allows bacteria to sense local population density in a process called
quorum sensing
Antigen receptors are generated by
random rearrangement of DNA
Selection of which chromosome forms the Barr body occurs
randomly and independently in each embryonic cell present at the time of X inactivation. The orange-and-black pattern on tortoiseshell cats is due to patches of cells expressing an orange allele while other patches have a non-orange allele.
Cleavage:
rapid mitotic cell division of the zygote that begins immediately after fertilization -Zygote cytoplasm partitioned into smaller cells (blastomeres) -Solid ball of cells = morula -Blastula (hollow ball of cells) filled with fluid (blastocoel) --Blastocyst (human)
Once secreted, local regulators act on their target cells quite
rapidly, even faster than hormones do.
Dominant alleles that cause a lethal disease are
rare and arise by mutation
Codons must be read in the correct
reading frame (correct groupings) in order for the specified polypeptide to be produced
The factor for white flowers was not diluted or destroyed because it
reappeared in the F2 generation
Which of the following are directly associated with photosystem I?
receiving electrons from the thylakoid membrane electron transport chain
Antigens are recognized by
receptor proteins on the lymphocyte membrane.
Helper T cells recognize the
receptor-antigen complex and activate the B cell, which divides and produces plasma and memory cells.
Lipid-soluble hormones bind to
receptors in the cytoplasm or nucleus of the target cells
Epinephrine binds to
receptors on the plasma membrane of liver cells
Translocations may be
reciprocal (two nonhomologous chromosomes exchange segments) or nonreciprocal (one chromosome transfers a segment without receiving one).
INNATE IMMUNITY (all animals)
recognition of traits shared by broad ranges of pathogens, using a small set of receptors; rapid response
ADAPTIVE IMMUNITY (vertebrates only)
recognition of traits specific to particular pathogens, using a vast array of receptors; slower response
Innate immune cells in mammals detect, devour, and destroy invading pathogens. These cells
recognize groups of pathogens via receptors that recognize fragments of molecules characteristic of a set of pathogens. (TLRs, or Toll-like receptors)
Crossing over produces
recombinant chromosomes, which combine DNA inherited from each parent
The fact that there are about a million different antigen receptors possible in human B cells is based on _____.
recombination of the segments of the receptor DNA that make up the functional receptor genes of differentiated B cells Which variable and which joining segments are recombined in the DNA of the differentiated B cells determine which receptor proteins will be made in that B cell.
During the Calvin cycle electrons stored in NADPH are used to
reduce carbon
Opening other types of ion channels triggers a depolarization, a
reduction in the magnitude of the membrane potential
In the process of carbon fixation, RuBP attaches a CO2 to produce a six-carbon molecule, which is then split to produce two molecules of 3-phosphoglycerate. After phosphorylation and reduction produces glyceraldehyde 3-phosphate (G3P), what more needs to happen to complete the Calvin cycle?
regeneration of RuBP
domains (proteins)
region of AA sequence that folds locally that has a particular function. Proteins often have a modular architecture consisting of discrete regions
Noncoding RNAs
regulate gene expression at two points: mRNA translation and chromatin configuration
Eukaryotic gene expression is
regulated at many stages
In multicellular eukaryotes, gene expression
regulates development and is responsible for differences in cell types
Phosphorylation and dephosphorylation of proteins is a widespread cellular mechanism for
regulating protein activity
Bacteria often respond to environmental change by
regulating transcription
The frequency of cell division varies with the type of cell. These differences result from
regulation at the molecular level
Ultimately, a signal transduction pathway leads to
regulation of one or more cellular activities
Cancer cells exhibit neither type of
regulation of their division
Hormones are assembled into
regulatory pathways
The initiation of translation of selected mRNAs can be blocked by
regulatory proteins that bind to sequences or structures of the mRNA
Positive feedback
reinforces a stimulus to produce an even greater response
chi square
relating to or denoting a statistical method assessing the goodness of fit between observed values and those expected theoretically.
Map units indicate
relative distance and order, not precise locations of genes
The ribosome and mRNA move
relative to each other, codon by codon
A small change in number of calcium ions thus represents a
relatively large percentage change in calcium concentration
In some cases, scaffolding proteins may also help activate some of the
relay proteins
The Ras protein is a G protein that
relays a signal from a growth factor receptor on the cell surface The response to the resulting cascade stimulates cell division
The A site accepts a protein called a
release factor
There are no tRNAs complementary to the three stop codons; termination occurs when
release factors recognize the stop codon in the A-site and catalyze the release of the polypeptide from the tRNA in the P-site.
Epinephrine binds to receptors on the plasma membrane of liver cells. This triggers the
release of messenger molecules that activate enzymes and result in the release of glucose into the bloodstream
Mucus traps and allows for the
removal of microbes
Deletion
removes a chromosomal segment
In mismatch repair of DNA,
repair enzymes correct errors in base pairing
Nucleosome
repeating subunit of chromatin fibers, consisting of DNA coiled around histones
Duplication
repeats a segment
A nucleotide-pair substitution
replaces one nucleotide and its partner with another pair of nucleotides
In binary fission, the chromosome
replicates (beginning at the origin of replication), and the two daughter chromosomes actively move apart
Along one template strand of DNA, the DNA polymerase synthesizes a leading strand continuously, moving toward the
replication fork
At the end of each replication bubble is a
replication fork, a Y-shaped region where new DNA strands are elongating
The action of helicase creates _____.
replication forks and replication bubbles A replication fork is the transition region between paired and unpaired DNA strands.
Like mitosis, meiosis is preceded by the
replication of chromosomes
In unicellular organisms, division of one cell
reproduces the entire organism
Genes are passed to the next generation via
reproductive cells called gametes (sperm and eggs)
The discovery of the genetic role of DNA began with
research by Frederick Griffith in 1928
Reduction of oxygen to form water occurs during ___ only
respiration
Photoreceptors
respond to light
External signals are converted to
responses within the cell
Ion pumps and ion channels establish the
resting potential of a neuron
After a response is triggered, the chemical synapse returns to its
resting state
Arousal and sleep are controlled in part by the
reticular formation, a network formed mainly of neurons in the midbrain and pons
Inversion
reverses orientation of a segment within a chromosome
The activity of a Cdk
rises and falls with changes in the concentration of its cyclin partner
In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?
roan * roan
Carbon fixation is catalyzed by
rubisco
Mendel's laws of segregation and independent assortment reflect the
rules of probability
Action potentials in myelinated axons jump between the nodes of Ranvier in a process called
saltatory conduction
Co-expressed eukaryotic genes can be
scattered over different chromosomes, but each has the same combination of control elements
Primase can start an RNA chain from
scratch and adds RNA nucleotides one at a time using the parental DNA as a template
Calcium ions (Ca2+) are used widely as a
second messenger
Many signaling pathways involve
second messengers
Memory cells enable the
secondary response
Mammary glands
secrete milk through nipples in breast
Cells of different mating types locate each other via
secreted factors specific to each type
paracrine signaling
secreted molecules diffuse locally and trigger a response in neighboring cells
Autocrine signaling
secreted molecules diffuse locally and trigger a response in the cells that secrete them
Antibodies have the same Y shape as B cell antigen receptors but are
secreted, not membrane bound
The humoral response is characterized by
secretion of antibodies by B cells
Nüsslein-Volhard and Wieschaus studied
segment formation
A cluster of functionally related genes can be coordinately controlled by a single "on-off switch." The switch is a
segment of DNA called an operator, usually positioned within the promoter
control elements
segments of noncoding DNA in eukaryotic genes that help regulate transcription by binding to certain proteins.
The length of time each protein functions is regulated by
selective degradation
true-breeding plants
self-pollinating, produce offspring identical to themselves
As lymphocytes mature in bone marrow or the thymus, they are tested for
self-reactivity
Experiments by Matthew Meselson and Franklin Stahl supported the
semiconservative model
Path of sperm travel
seminiferous tubules 🡪 epididymis 🡪 vas deferens 🡪 urethra (penis)
The midbrain receives and integrates
sensory information and sends it to specific regions of the brain
Nervous systems process information in three stages:
sensory input, integration, and motor output
During cell division, the two sister chromatids of each duplicated chromosome
separate and move into two nuclei
In calculating the chances for various genotypes, each character is considered
separately, and then the individual probabilities are multiplied
MEIOSIS II:
separates sister chromatids
Transduction often occurs in a
series of steps
The medulla is also in control of
several automatic functions such as breathing, heart and blood vessel activity, swallowing, vomiting, and digestion
Many Y-linked genes are related to
sex determination
SRY
sex determining region of the Y chromosome
A gene that is located on either sex chromosome is called a
sex-linked gene
Fertilization and meiosis alternate in
sexual life cycles
Primary structure in turn determines
shape
At each step, the signal is transduced into a different form, usually a
shape change in a protein
The initial nucleotide strand is a
short RNA primer
In other cases, animal cells communicate using secreted messenger molecules that travel only
short distances
Telomeres do not prevent the
shortening of DNA molecules
Binding of a hormone to its receptor initiates a
signal transduction pathway leading to responses in the cytoskeleton, enzyme activation, or a change in gene expression
Cells in a multicellular organism communicate via
signaling molecules
Different proteins allow cells to detect and respond to different
signals
Second messengers transfer and amplify
signals from receptors to proteins that cause responses
Genes are turned on and off in response to
signals from their external and internal environments
Genomic imprinting involves the
silencing of certain genes depending on which parent passes them on
Innate defenses of mammals are ___ to those of invertebrates
similar
G proteins are all very
similar in structure
Small interfering RNAs (siRNAs) are
similar to miRNAs in size and function
Inheritance patterns are often more complex than predicted by
simple Mendelian genetics
Translation of all mRNAs in a cell may be regulated ___
simultaneously
Mendel derived the law of segregation by following a
single character
A gamete (sperm or egg) contains a
single set of chromosomes and is thus a haploid cell (n)
Each duplicated chromosome has two
sister chromatids (joined copies of the original chromosome)
In anaphase II
sister chromatids separate The sister chromatids of each chromosome now move as two newly individual chromosomes toward opposite poles
Sister chromatid cohesion allows
sister chromatids to stay together through meiosis I
Seminiferous tubules
site of sperm production
Mendel observed the same pattern of inheritance in
six other pea plant characters, each represented by two traits
The cerebrum controls
skeletal muscle contraction and is the center for learning, emotion, memory, and perception
Barrier defenses include the
skin and mucous membranes of the respiratory, urinary, and reproductive tracts
Spliceosomes are complexes composed of
small RNAs and proteins
Mitochondria, chloroplasts, and other plant plastids carry
small circular DNA molecules
___ or ___ chemical messengers can readily cross the membrane and activate receptors
small or hydrophobic
In most cases, the ligands of intracellular receptors are
small, hydrophobic (water-hating) molecules, since they must be able to cross the plasma membrane in order to reach their receptors.
MicroRNAs (miRNAs) are
small, single-stranded RNA molecules that can bind complementary sequences in mRNA
morula
solid ball of cells
Humans have 46 chromosomes in the nuclei of their
somatic cells, all cells of the body except gametes and their precursors
Action potentials arise because
some ion channels are voltage-gated, opening or closing when the membrane potential passes a certain level called threshold
When Griffith mixed heat-killed remains of the pathogenic strain with living cells of the harmless strain, what happened?
some living cells became pathogenic He called this phenomenon transformation
Alterations of chromosome number and structure are associated with
some serious disorders
During prometaphase
some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes
Most water-soluble signal molecules bind to specific sites on receptor proteins that
span the plasma membrane
In synaptic signaling, neurons form
specialized junctions with target cells, called synapses
In the cell-mediated immune response
specialized T cells destroy infected host cells
The nervous system is a network of
specialized cells—neurons—that transmit signals along dedicated pathways
The binding between a signal molecule (ligand) and receptor is highly
specific
Each tRNA molecule carries a
specific amino acid on one end and an anticodon on the other end
The cell cycle appears to be driven by
specific chemical signals present in the cytoplasm
Activator proteins in the nucleus recognize
specific control elements and promote simultaneous transcription of the genes
The syndrome cri du chat ("cry of the cat"), results from a
specific deletion in chromosome 5
External factors that influence cell division include
specific growth factors
When a signal molecule binds as a ligand to the receptor, the gate allows
specific ions, such as Na+ or Ca2+, through a channel in the receptor
The information content of genes is in the
specific sequences of nucleotides
Each individual B or T cell is specialized to recognize a
specific type of molecule
Fertilization =
sperm + egg
Male reproductive system: role of FSH?
sperm formation
In some cases, RNA splicing is carried out by
spliceosomes
The RNAs of the spliceosome also catalyze the
splicing reaction
Large-scale chromosomal alterations in humans and other mammals often lead to
spontaneous abortions (miscarriages) or cause a variety of developmental disorders
Cancer can be caused by mutations to genes that normally regulate cell growth and division. Mutations in these genes can be caused by
spontaneous mutation or environmental influences such as chemicals, radiation, and some viruses
blastocyst
stage of early development in mammals that consists of a hollow ball of cells
Some inheritance patterns are exceptions to
standard Mendelian inheritance
The primer's 3′ end serves as the
starting point for the new DNA strand
Myoblasts
stem cells that fused to form each muscle fiber early in development
Examples of hydrophobic messengers are the
steroid and thyroid hormones of animals
Lipid-soluble hormones
steroid hormones, thyroid hormones, nitric oxide
The other 3 triplet codons act as
stop signals (UAA, UAG and UGA) and mark where ribosomes end translation. AUG acts as a start signal but it also codes for methionine.
Evolution has resulted in a close match between
structure and function
Basal ganglia
structures in the forebrain that help to control movement Below the corpus callosum and cerebral cortex. A collation of nuclei (neurons that have the same function). Regulates motor control.
More evidence for DNA as the genetic material came from
studies of viruses that infect bacteria
The first evidence of extranuclear genes came from
studies on the inheritance of yellow or white patches on leaves of an otherwise green plant
A corepressor is a
substance that inhibits the expression of genes. inducible operon, regulatory repressor protein is normally bound to the operator, which prevents the transcription of the genes on the operon. molecule that cooperates with a repressor protein to switch an operon off
Other pathways may regulate the activity of enzymes rather than their
synthesis For example, a signal could cause opening or closing of an ion channel in the plasma membrane or a change in cell metabolism
Transcription
synthesis of an RNA molecule from a DNA template
The DNA inherited by an organism leads to specific traits by dictating the
synthesis of proteins
Ribosomes facilitate specific coupling of
tRNA anticodons with mRNA condons in protein synthesis
The location of a particular gene can be seen by
tagging isolated chromosomes with a fluorescent dye that highlights the gene
Reception (signal transduction pathway)
target cell's detection of a signaling molecule coming from outside the cell; The binding between a signal molecule (ligand) and receptor is highly specific (lock & key) and generally causes a shape change in the receptor, activating the receptor A signaling molecule binds to a receptor protein, causing it to change shape
Hormones reach all parts of the body, but only
target cells have receptors for that hormone
Hormones and other signaling molecules bind to
target receptors, triggering specific response pathways
Forebrain
telencephalon and diencephalon
The forebrain divides into the
telencephalon and diencephalon
Eukaryotic chromosomal DNA molecules have special nucleotide sequences at their ends called
telomeres
Since the two strands of DNA are complementary, each strand acts as a
template for building a new strand in replication
If two EPSPs are produced in rapid succession, an effect called
temporal summation occurs
The refractory period is a result of a
temporary inactivation of the Na+ channels
Male reproductive system main reproductive organs
testes
Male reproductive system main hormone?
testosterone
The diencephalon develops into
thalamus, hypothalamus, epithalamus
The diencephalon gives rise to the
thalamus, hypothalamus, epithalamus
Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest?
that the parents were both heterozygous for a single trait
The first step of DNA replication is
the DNA double helix is "unzipped" or separated when an enzyme breaks hydrogen bonds between nitrogen bases (helicase)
The changes in the enzyme and G protein are only temporary because
the G protein also functions as a GTPase enzyme—in other words, it then hydrolyzes its bound GTP to GDP. Now inactive again, the G protein leaves the enzyme, which returns to its original state. The G protein is now available for reuse. The GTPase function of the G protein allows the pathway to shut down rapidly when the signaling molecule is no longer present.
Given the damage caused by UV radiation, the kind of gene affected in those with XP is one whose product is involved with
the ability to excise single-strand damage and replace it.
Fertilization
the action or process of fertilizing an egg, female animal, or plant, involving the fusion of male and female gametes to form a zygote.
Each codon specifies
the amino acid (one of 20) to be placed at the corresponding position along a polypeptide
In Drosophila, cytoplasmic determinants in the unfertilized egg determine
the axes before fertilization
genes
the biochemical units of heredity that make up the chromosomes; a segment of DNA capable of synthesizing a protein
Hormones secreted into extracellular fluids by endocrine cells reach their targets via
the bloodstream
A reflex is
the body's automatic response to a stimulus (the information is processed at the level of the spinal cord; it never goes to the brain)
The clock has specific checkpoints where
the cell cycle stops until a go-ahead signal is received
The spindle includes the
the centrosomes, the spindle microtubules, and the asters
The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span. The region that spans the membrane is an
the chloroplast membrane ion channel through which protons can pass.
At metaphase
the chromosomes are all lined up at the metaphase plate, a plane midway between the spindle's two poles
No chromosome replication occurs between the end of meiosis I and the beginning of meiosis II because
the chromosomes are already replicated
Thomas Hunt Morgan's early experiments provided convincing evidence that
the chromosomes are the location of Mendel's heritable factors
In telophase II
the chromosomes arrive at opposite poles Nuclei form, and the chromosomes begin decondensing
In anaphase
the cohesins are cleaved by an enzyme called separase Sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell. The microtubules shorten by depolymerizing at their kinetochore ends
Morgan proposed that some process must occasionally break the physical connection between genes on the same chromosome. This mechanism was
the crossing over of homologous chromosomes
All 64 codons were deciphered in
the early 1960s
At electrical synapses,
the electrical current flows from one neuron to another through gap junctions
An operon is
the entire stretch of DNA that includes the operator, the promoter, and the genes that they control
Exon shuffling may result in the
the evolution of new proteins
E site
the exit site, where discharged tRNAs leave the ribosome
nondisjunction
the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.
Estrous cycle
the female reproductive cycle of mammals other than primates; no menstruation
The chemiosmotic hypothesis states that
the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP
blastocoel
the fluid-filled cavity of a blastula
The inflammatory response continues until
the foreign material is eliminated and the wound is repaired
The synthesis of a DNA strand begins with
the formation of an RNA primer. (primase)
one gene-one enzyme hypothesis
the function of a gene is to dictate production of a specific enzyme
Sturtevant and his colleagues found that
the genes clustered into four groups of linked genes (linkage groups). The linkage maps, combined with the fact that there are four chromosomes in Drosophila, provided additional evidence that genes are located on chromosomes
When the SRY gene is absent
the gonads of the embryo develop into ovaries (female gonads)
Density-dependent inhibition and anchorage dependence check
the growth of cells at an optimal density
Sturtevant predicted that the farther apart two genes are
the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency
Most polyploid plants are the result of
the hybridization of two different parental species.
Cell-cell recognition is important in
the immune response and embryonic development
Large ribosomal subunit completes
the initiation complex
When the bacteria had been infected with T2 phage whose DNA was tagged with radioactive phosphorus, the pellet of mainly bacterial material contained most of the radioactivity, indicating that
the labeled phage DNA had entered the cells.
heavy chains
the larger of the two component polypeptides of an immunoglobulin molecule. Heavy chains come in a variety of heavy-chain classes or isotypes, each of which confers a distinctive effector function on the antibody molecule. The constant (C) regions of the chains vary little among B cells, whereas the variable (V) regions differ greatly
Limitations of DNA polymerase create problems for
the linear DNA of eukaryotic chromosomes
A knock-out mutation refers to
the loss of a protein's function but not necessarily to its complete absence.
equilibrium potential
the magnitude of the membrane voltage at equilibrium for a particular ion
"Pac-man" mechanism
the microtubule minus-end remains fixed at the pole, the kinetochore translocates at the depolymerizing microtubule plus end, as if it "chews" its way to the pole by itself.
Mesoderm
the middle layer of an embryo in early development, between the endoderm and ectoderm. -Skeletal, muscular systems -Notochord -Excretory, circulatory -Reproductive system -Blood, bone, muscle
The centromere is the
the narrow "waist" of the duplicated chromosome, where the two chromatids are most closely attached
The nontemplate strand is called the coding strand because
the nucleotides of this strand are identical to the codons, except that T is present in the DNA in place of U in the RNA
Oxytocin secretion and milk release from the mammary glands of lactating female mammals are initiated by
the physical sensation of the baby sucking at the nipple The milk-release response system was given as an example of a neuroendocrine pathway with positive feedback leading to milk release from the nursing mother to the sucking baby. The "neuro" part includes the baby's activation of the mother's mechanoreceptor neurons in the breast.
The addition rule states that
the probability that any one of two or more mutually exclusive events will occur is calculated by adding together their individual probabilities
Negative feedback mechanism in gene expression
the product produced binds to the enzyme to inhibit its activity; the final product controls the amount of product that is created, and when the amount of product in the cell gets too much, its production is limited by the product itself.
genetic recombination
the production of offspring with combinations of traits that differ from those found in either parent
Spermatogenesis
the production of sperm cells -Sperm production -Stem cells 🡪 spermatids in seminiferous tubules -Mature & add tail in epidymis -4 motile sperm
Proximal control elements are located close to
the promoter
Comparison of vertebrates shows that relative sizes of particular brain regions vary. These size differences reflect
the relative importance of the particular brain function
The continuity of life is based on
the reproduction of cells, or cell division
Translocation is the process by which
the ribosome slides down the mRNA so a new cycle of elongation can begin. The ribosome slides one codon down the mRNA.
The template strand is always ___ strand for a given gene
the same
peripheral nervous system (PNS)
the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.
Passive immunity
the short-term immunity that results from the introduction of antibodies from another person or animal. provides immediate, short-term protection
The genetic code is nearly universal, shared by
the simplest bacteria and the most complex animals
In metaphase II
the sister chromatids are arranged at the metaphase plate The kinetochores of sister chromatids attach to microtubules extending from opposite poles
In a simple neuroendocrine pathway
the stimulus is received by a sensory neuron, which stimulates a neurosecretory cell. The neurosecretory cell secretes a neurohormone, which enters the bloodstream and travels to target cells
coding strand
the strand of DNA that is not used for transcription and is identical in sequence to mRNA because it is complementary to the template strand, except it contains uracil instead of thymine
transcription unit
the stretch of DNA that is transcribed into an RNA molecule
In mitochondria, chemiosmosis translocates protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis translocates protons from
the stroma to the thylakoid space
Sickle cell disease is caused by
the substitution of a single amino acid in the hemoglobin protein in red blood cells In homozygous individuals, all hemoglobin is abnormal (sickle-cell) Symptoms include physical weakness, pain, organ damage, and even paralysis
Sickle cell is caused by
the substitution of a single amino acid in the hemoglobin protein in red blood cells (valine for glutamatic acid)
Translation
the synthesis of a polypeptide, using information in the mRNA; Process by which mRNA is decoded and a protein is produced
During the rising phase
the threshold is crossed, and the membrane potential increases
Heredity
the transmission of traits from one generation to the next
The chromosomal basis of Mendel's law of segregation state that
the two alleles for each gene separate during gamete formation.
semiconservative model
the two strands of the parental molecule separate, and each functions as a template for synthesis of a new, complementary strand
Genes
the units of heredity and are made up of segments of DNA
The X-ray images also enabled Watson to deduce
the width of the helix and the spacing of the nitrogenous bases The pattern in the photo suggested that the DNA molecule was made up of two strands, forming a double helix
Extranuclear genes are inherited maternally because
the zygote's cytoplasm comes from the egg
Sister chromatids are attached along
their lengths by cohesins
Neurons carry out their specialized functions of communication and integration because
their outer cell membrane has special properties
Heterozygotes are less susceptible to the malaria parasite, so
there is an advantage to being heterozygous in regions where malaria is common
As in all cells, the cell membrane of a neuron is polarized. This means that
there is an electrical difference across the cell membrane.
Linked genes tend to be inherited together because
they are located near each other on the same chromosome
Why are cell cycle kinases considered cyclin-dependent kinases?
they require attachment to a cyclin in order to be activated. The activity of a CdK rises and falls with changes in the concentration of its cyclin partner.
chromosomes
threadlike structures made of DNA molecules that contain the genes
Mendel discovered a ratio of about
three to one, purple to white flowers, in the F2 generation
After DNA was accepted as the genetic material, the challenge was
to determine how its structure accounts for its role in heredity
Why did Mendel continue some of his experiments to the F2 or F3 generation?
to observe whether or not a recessive trait would reappear
Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that
traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.
Gene expression is regulated at many stages, but is often equated with
transcription
A bacterial cell ensures a streamlined process by coupling
transcription and translation In this case the newly made protein can quickly diffuse to its site of function
Gene expression, the process by which DNA directs protein synthesis, includes two stages:
transcription and translation
Genes specify proteins via
transcription and translation
The final activated molecule in the signaling pathway may function as a
transcription factor
RNA polymerase requires the assistance of
transcription factors to initiate transcription
A repressible operon is
transcription is usually on, but can be inhibited (repressed) when a specific small molecule binds allosterically to a regulatory protein (example tryptophan) one that is usually on; binding of a repressor to the operator shuts off transcription
General transcription factors are essential for the
transcription of all protein-coding genes
When a steroid hormone binds to its cytosolic receptor, a hormone-receptor complex forms that moves into the nucleus. There, the receptor part of the complex acts as a
transcriptional regulator of specific target genes
Promoters signal the
transcriptional start point and usually extend several dozen nucleotide pairs upstream of the start point
A cell translates an mRNA message into protein with the help of
transfer RNA (tRNA)
tRNA
transfer RNA; type of RNA that carries amino acids to the ribosome
A major function of the pons and medulla is to
transfer information between the PNS and the midbrain and forebrain
Self-pollinate
transfer of pollen from an anther to a stigma of the same flower
Cells that acquire the ability to divide indefinitely are undergoing
transformation
Genetic information flows from mRNA to protein through the process of
translation
The start codon (AUG) signals the start of
translation
Sensory neurons
transmit information about external stimuli such as light, touch, or smell
Motor neurons
transmit signals to muscle cells, causing them to contract
The axon is typically a much longer extension that
transmits signals to other cells at synapses
Genes can be transcribed and translated after being
transplanted from one species to another
Lymphatic ducts function in the
transport of lymphocytes throughout the body.
A single EPSP is usually too small to
trigger an action potential in a postsynaptic neuron
A receptor tyrosine kinase can
trigger multiple signal transduction pathways at once
MPF (maturation-promoting factor) is a cyclin-Cdk complex that
triggers a cell's passage past the G2 checkpoint into the M phase
In response, the transduced signal
triggers a specific response in the target cell
Mast cells, immune cells found in connective tissue, release histamine, which
triggers blood vessels to dilate and become more permeable
The flow of information from gene to protein is based on a
triplet code
Unlike homozygotes, heterozygotes are not
true-breeding
He also started with varieties that were
true-breeding (plants that produce offspring of the same variety when they self-pollinate)
A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the "1" in the 9:3:3:1 ratio)?
ttpp
Cancer cells that are not eliminated by the immune system form
tumors, masses of abnormal cells within otherwise normal tissue
Many signaling pathways regulate the synthesis of enzymes or other proteins, usually by
turning genes on or off in the nucleus
Because of hydrogen bonds, tRNA
twists and folds into a three-dimensional molecule
Most genes exist in populations in more than
two allelic forms For example, the four phenotypes of the ABO blood group in humans are determined by three alleles for the enzyme that attaches A or B carbohydrates to red blood cells: IA, IB, and i. The enzyme encoded by the IA allele adds the A carbohydrate, whereas the enzyme encoded by the IB allele adds the B carbohydrate; the enzyme encoded by the i allele adds neither.
If a recessive allele that causes a disease is rare, it is unlikely that
two carriers will meet and mate
The centrosome replicates during interphase, forming
two centrosomes that migrate to opposite ends of the cell during prophase and prometaphase
A dihybrid cross, a cross between F1 dihybrids, can determine whether
two characters are transmitted to offspring as a package or independently
Mendel identified his second law of inheritance by following
two characters at the same time
Polyploidy is a condition in which an organism has more than
two complete sets of chromosomes
In a typical experiment, Mendel mated
two contrasting, true-breeding varieties, a process called hybridization
Most cell division results in
two daughter cells with identical genetic information
Each T cell receptor consists of
two different polypeptide chains (called α and β) The tips of the chain form a variable (V) region; the rest is a constant (C) region
Each replicated chromosome consists of
two identical sister chromatids
Mendel used the scientific approach to identify
two laws of inheritance
A multicharacter cross is equivalent to
two or more independent monohybrid crosses occurring simultaneously
Rosalind Franklin had concluded that there were
two outer sugar-phosphate backbones, with the nitrogenous bases paired in the molecule's interior
A diploid cell (2n) has
two sets of chromosomes
Somatic cells (nonreproductive cells) have
two sets of chromosomes
At the end of telophase I and cytokinesis, there are two haploid cells with chromosomes that consist of
two sister chromatids each.
The adaptive response relies on
two types of lymphocytes, or white blood cells
sexual reproduction
type of reproduction in which cells from two parents unite to form the first cell of a new organism; genetic diversity
Cells mark proteins for degradation by attaching
ubiquitin to them
Various procedures can be used to detect genetic disorders before birth. Among the tests discussed in this chapter, which is the least invasive (list first), and which two allow the chromosomes of the fetus to be examined?
ultrasound imaging ... chorionic villus sampling ... amniocentesis
Each zygote has a
unique genetic identity
Sex-linked genes exhibit
unique patterns of inheritance
Offspring resemble their parents more than they do
unrelated individuals
Nucleotide sequences that influence the life span of mRNA in eukaryotes reside in the
untranslated region (UTR) at the 3′ end of the molecule
RNA synthesis follows the same base-pairing rules as DNA, except that
uracil substitutes for thymine
Cancer cells manage to escape the
usual controls on the cell cycle
Heterozygotes (said to have sickle-cell trait) are
usually healthy but may suffer some symptoms
Genes within highly packed heterochromatin are
usually not expressed
Hormones that promote homeostasis
usually operate as part of a negative feedback system
Random fertilization increases even further the number of
variant combinations that can be produced
Alternative versions of genes account for
variations in inherited characters
Mendel chose to track only those characters that
varied in an "either or" manner occurred in two distinct alternative forms
Peas were available to Mendel in many different
varieties
Regulatory mechanisms can operate at
various stages after transcription
Comparison of vertebrates shows that relative sizes of particular brain regions
vary
Because there are so few Y-linked genes
very few disorders are transferred from father to son on the Y chromosome
Molecular details of signal transduction in yeasts and mammals are
very similar.
Sound receptors respond to
vibration
In neutralization, antibodies bind to
viral surface proteins, preventing infection of a host cell
During the falling phase
voltage-gated Na+ channels become inactivated; voltage-gated K+ channels open, and K+ flows out of the cell
During the light reactions of photosynthesis, ___ ___ ___ , and during the Calvin cycle, ___ ___ ___
water is oxidized carbon is reduced.
Polypeptides and most amines are
water soluble
Watson and Crick's semiconservative model of replication predicts that
when a double helix replicates, each daughter molecule will have one old strand (derived or "conserved" from the parent molecule) and one newly made strand
Positive Gene Regulation
when a regulatory protein interacts directly with the genome to switch transcription on When glucose (a preferred food source of E. coli) is scarce, CRP is activated by binding with cyclic AMP (cAMP) Activated CRP attaches to the promoter of the lac operon and increases the affinity of RNA polymerase, thus accelerating transcription When glucose levels increase, CRP detaches from the lac operon, and transcription returns to a normal rate CRP helps regulate other operons that encode enzymes used in catabolic pathways
Growth factors act as signals telling the cell
when to move through the cell cycle as well as when to divide.
For a growing number of diseases, tests are available that identify carriers and help define the odds more accurately. The tests enable people to make more informed decisions about having children. However, they raise other issues, such as
whether affected individuals fully understand their genetic test results, and how the test results are used
The ability of a cell to respond to a hormone signal depends on
whether or not it has a receptor specific to that signal
The compounds present in any given cell determine
which genes are switched on
For a few mammalian traits, the phenotype depends on
which parent passed along the alleles for those traits
Some genes can encode more than one kind of polypeptide, depending on
which segments are treated as exons during splicing
Growth factors, which stimulate ... are one class of such ... in animals
which stimulate nearby target cells to grow and divide, are one class of such local regulators in animals
In this experiment, Engelmann was able to determine
which wavelengths (colors) of light are most effective at driving photosynthesis.
Cyclic AMP (cAMP) is one of the most
widely used second messengers
Flexible pairing at the third base of a codon is called
wobble and allows some tRNAs to bind to more than one codon
Growth factors are considered an external chemical regulatory cue because they
work from the outside of the cell.
To elongate the other new strand, called the lagging strand, DNA polymerase must
work in the direction away from the replication fork
The fertilized egg is called a ___ and has
zygote; has one set of chromosomes from each parent
Distinguish between introns and exons. Perhaps it will help to remember this: Exons are expressed.
"Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that lie between coding regions." Introns are intervening sequences (noncoding regions). Exons are expressed sequences and they are usually translated into amino acid sequences. "RNA splicing removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence."
The hormone epinephrine has multiple effects that form the basis of the
"fight-or-flight" response
In the past, genes that did not encode a protein product or known functional RNA were considered
"junk DNA" A flood of recent data has contradicted this idea
MyoD is a
"master regulatory gene" that encodes a transcription factor that commits the cell to becoming skeletal muscle
The cell's response to an extracellular signal is called the
"output response"
Coupled with the ability to sequence the DNA of cells in a particular tumor, treatments are becoming more
"personalized"
Cells that are infected, damaged, or at the end of their functional lives often undergo
"programmed cell death"
Results of a clever experiment suggest that motor proteins on kinetochores
"walk" the chromosomes along the microtubules during anaphase The depolymerization of the microtubules at the kinetochore ends occurs after the motor proteins have passed
haploid cell
A cell containing only one set of chromosomes (n).
Second messengers participate in pathways initiated by
GPCRs and RTKs
terminator
In bacteria, the sequence signaling the end of transcription
Fertilization is the
Union of gametes.
If DNA is irreparable, p53 activates
cell "suicide" genes
In density-dependent inhibition,
crowded cells stop dividing
Specific brain structures are particularly specialized for
diverse functions
How many origins of replication do eukaryotes have?
hundreds or even thousands
The trp operon is a
negative repressible operon
Normal p53 prevents a cell from
passing on mutations
Most genes are
pleiotropic
Cell signaling is critical among
prokaryotes
The vertebrate brain is
regionally specialized
MEIOSIS I:
separates homologous chromosomes
Checkpoints also register
signals from outside the cell
An activated B cell gives rise to
thousands of identical plasma cells
If both members of the couple had a sibling with the recessively inherited illness, both of their parents were carriers. Thus each has a ___ chance of being a carrier. If both are carriers, there is a ___ chance of each child having the recessive illness. The overall probability of them having a child with the illness is ___ × ___ × ___ = ___
⅔ ¼ ⅔ * ⅔ * ¼ = 1/9
In the humoral immune response
antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph
Myelin sheaths are made by glia—
Oligodendrocytes (CNS) and Schwann cells (PNS)
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?
One addition and one deletion mutation. This combination results in no net change in the number of bases, so the reading frame would eventually be restored.
Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties?
One allele was dominant.
There are two normally occurring exceptions to Mendelian genetics. They are:
One exception involves genes located in the nucleus, and the other involves genes located outside the nucleus. In both cases, the sex of the parent contributing an allele is a factor in the pattern of inheritance
The Watson-Crick model explains Chargaff's rules:
in any organism the amount of A = T, and the amount of G = C
The septum is involved in
in emotionally significant learning and the sensation of pleasure.
Since DNA polymerase can assemble DNA only in the 5' to 3' direction, the new strand complementary to the 3' to 5' strand must be assembled either
in short 5' to 3' segments, which are later joined together by ligase, or be assembled continuously
Neurotransmitter binding causes
ion channels to open, generating a postsynaptic potential
When voltage-gated ion channels open
ions flow though channel
Throughout this course, we have emphasized feedback loops. Explain how a feedback loop functions.
Feedback loops link the response back to the initial stimulus as a means of regulating pathways. The response pathway for many hormones involves negative feedback (the response reduces the initial stimulus). Negative feedback regulates excessive pathway activity. Positive feedback, on the other hand, reinforces a stimulus and thus increases a response.
What is an anticodon?
The sequence that is complementary to the codon of the mRNA. An anticodon is found on the tRNA molecule.
Direction a signal travels through the nervous system
The signal is transmitted to the dendrites which then transmits it through the axon and then sends it to the postsynaptic neuron- the signal then exits the postsynaptic neuron from the synaptic terminals.
Density-dependent inhibition and anchorage dependence check the growth of cells at an
optimal density
A karyotype is an
ordered display of the pairs of chromosomes in metaphase from a cell
Extranuclear genes (or cytoplasmic genes) are found in
organelles in the cytoplasm
Replication begins at particular sites called
origins of replication, where the two DNA strands are separated, opening up a replication "bubble"
Cells can signal to each other and interpret the signals they receive from
other cells and the environment
Neurons communicate with
other cells at synapses
Estrous cycle is seen in
other mammals
K+ diffuses ___ of the neuron
out
We can apply the rules of probability to predict the
outcome of crosses involving multiple characters
Ectoderm
outermost germ layer; produces sense organs, nerves, and outer layer of skin -Skin, nails, teeth -Lens of eye -Nervous system (brain, spinal cord)
In a resting neuron, the
outside of the membrane is positively charged relative to the inside of the membrane (remember that there are many negatively charged anions within the cell).
Apoptosis can be triggered by signals from
outside the cell or inside it
Histone tails protrude
outward from a nucleosome.
Female reproductive system main reproductive organs
ovaries
Female Anatomy
ovaries - contain follicles + an egg fallopian tubes uterus cervix vagina breasts mammary glands
An organism's phenotype reflects its
overall genotype and unique environmental history
The SCN acts as a
pacemaker, synchronizing the biological clock
In nondisjunction,
pairs of homologous chromosomes do not separate normally during meiosis
A potato left growing in darkness produces
pale stems, unexpanded leaves, and short roots
List two types of local signaling that involve local regulators.
paracrine signaling; synaptic signaling
fission
parent separates into 2+ individuals of same size
Offspring with a phenotype matching one of the parental (P) phenotypes are called
parental types
The "particulate" hypothesis is the idea that
parents pass on discrete heritable units (genes)
Signaling substances in the cytosol can
pass freely between adjacent cells
Although the chromatin modifications just discussed do not alter DNA sequence, they may be
passed to future generations of cells
In adaptive immunity, receptors provide
pathogen-specific recognition
The life span of mRNA molecules in the cytoplasm is important in determining the
pattern of protein synthesis in a cell
Nucleotides consist of
pentose sugar, nitrogenous base, phosphate group
monohybrid cross
A cross between two individuals, concentrating on only one definable trait A cross between individuals that involves one pair of contrasting traits
Barr body
A dense body formed from a deactivated X chromosome.
What do we mean when we use the terms monohybrid cross and dihybrid cross?
A dihybrid cross involves organisms that are heterozygous for two characters and a monohybrid cross involves only one.
Movement of the chromosomes during anaphase would be most affected by a drug that prevents
shortening of microtubules.
The usual replication machinery provides no way to complete the 5′ ends, so repeated rounds of replication produce
shorter DNA molecules with uneven ends This is not a problem for prokaryotes, most of which have circular chromosomes
George Beadle and Edward Tatum
showed that genes encode a cell's enzymes exposed bread mold to X-rays, creating mutants that were unable to survive on minimal media
Scaffolding proteins can increase the
signal transduction efficiency by grouping together different proteins involved in the same pathway
induction
signal molecules from embryonic cells cause changes in nearby target cells
Signal transduction pathways link
signal reception with cellular response
Short segments at the ends of the Y chromosomes are homologous with the
X, allowing the two to behave like homologs during meiosis in males
Genes on the X chromosome are called
X-linked genes
Rosalind Franklin produced a picture of the DNA molecule using
X-ray crystallography
Maurice Wilkins and Rosalind Franklin were using a technique called
X-ray crystallography to study molecular structure
chiasmata
X-shaped regions where crossing over occurred.
Monosomy X, called Turner syndrome, produces
X0 females, who are sterile
In infected cells, MHC molecules bind and transport antigen fragments to the cell surface, a process called antigen presentation. A T cell can then bind both the
antigen fragment and the MHC molecule This interaction is necessary for the T cell to participate in the adaptive immune response
An activator is
a protein that binds to an enhancer and stimulates transcription of a gene
SRY codes for
a protein that regulates other genes.
T cells bind to
antigen fragments displayed or presented on a host cell
MHC molecules are host proteins that display the
antigen fragments on the cell surface
T or B cells bind to antigens via
antigen receptors specific to part of one molecule of that pathogen
The variable regions of a B cell provide
antigen specificity
Hemocytes also secrete
antimicrobial peptides that disrupt the plasma membranes of fungi and bacteria
Watson built a model in which the backbones were
antiparallel (their subunits run in opposite directions)
Like a new strand of DNA, the RNA molecule is synthesized in an
antiparallel direction to the template strand of DNA
All organisms must regulate which genes are expressed at
any given time
In the body there are few lymphocytes with antigen receptors for
any particular epitope
The combination of EPSPs through spatial and temporal summation can trigger an
action potential
What is an alternative version of a gene called?
allele
Mutations create different versions of genes called
alleles
During RNA processing, both ends of the primary transcript are
altered Also, in most cases, certain interior sections of the molecule are cut out and the remaining parts spliced together
Plants receive signals from the environment and respond by
altering growth and development
In epistasis, expression of a gene at one locus
alters the phenotypic expression of a gene at a second locus
Proteins are composed of
amino acid monomers
tRNAs transfer
amino acids to the growing polypeptide in a ribosome
Acetylcholine is just one of more than 100 known neurotransmitters. The remainder fall into four classes:
amino acids, biogenic amines, neuropeptides, and gases
a correct match between a tRNA and an amino acid is done by
aminoacyl-tRNA synthetase
Multistep pathways can greatly
amplify the signal
Random fertilization adds to genetic variation because
any sperm can fuse with any ovum
In humans and other mammals, several different pathways, including about 15 caspases, can carry out
apoptosis
Some B and T cells with receptors specific for the body's own molecules are destroyed by
apoptosis, or programmed cell death The remainder are rendered nonfunctional
Hormone X activates the cAMP second messenger system in its target cells. The greatest response by a cell would come from
applying a molecule of hormone X to the extracellular fluid surrounding the cell.
The brainstem and cerebrum control
arousal and sleep
Platelet-derived growth factor (PDGF) is made by
blood cell fragments called platelets
Paracrine and autocrine signaling play roles in processes such as
blood pressure regulation, nervous system function, and reproduction
The K+ and Na+ concentration gradients of the neurons represent
chemical potential energy
Animal hormones are
chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body
Most synapses are
chemical synapses
Chemoreceptors respond to
chemicals
Signals are most often
chemicals
Members of some animal species may communicate with pheromones,
chemicals that are released into the environment
To treat metastatic cancers
chemotherapies that target the cell cycle may be used
The addition of methyl groups (methylation) can
condense chromatin and reduce transcription
Polyploidy
condition in which an organism has extra sets of chromosomes
Action potentials are the signals
conducted by axons
Spliceosomes
consist of a variety of proteins and several small nuclear ribonucleoproteins (snRNPs) that recognize the splice sites
central nervous system (CNS)
consists of the brain and spinal cord
Action potentials have a
constant magnitude, are all-or-none, and transmit signals over long distances
In multicellular organisms, regulation of gene expression is
essential for cell specialization
If chromosomes of germ cells became shorter in every cell cycle,
essential genes would eventually be missing from the gametes they produce
What does the chemiosmotic process in chloroplasts involve?
establishment of a proton gradient across the thylakoid membrane
In animals, pattern formation begins with the
establishment of the major axes
All the DNA in a cell constitutes the cell's
genome
Proteins are the links between
genotype and phenotype
exocrine glands
gland that releases its secretions through tubelike structures called ducts
endocrine glands
glands that secrete chemicals called hormones directly into the bloodstream
Most neurons are nourished or insulated by cells called
glia, or glial cells
In the Calvin cycle, carbon dioxide (CO2), which enters the leaf as a gas, is converted into the simple sugar
glyceraldehyde-3-phosphate (G3P).
Generating and experiencing emotion often require
interactions between different parts of the brain
Spontaneous mutations can occur during
DNA replication, recombination, or repair
Offspring with nonparental phenotypes (new combinations of traits) are called
recombinant types, or recombinants
The true-breeding parents are the
P generation
mismatch repair
The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides.
Pattern formation
The development of a spatial organization of tissues and organs.
A plant has a unique photosynthetic pigment. The leaves of this plant appear to be reddish yellow. What wavelengths of visible light are being absorbed by this pigment?
blue and violet
Most individuals with recessive disorders are born to
carrier parents
Many signals registered at checkpoints come from
cellular surveillance mechanisms within the cell
G1 (first gap)
centers on growth; produces organelles
The rest of the hindbrain gives rise to the
cerebellum
DNA molecules in a cell are packaged into
chromosomes
Disruptions in immune system function can
elicit or exacerbate disease
As in all cells, the cell membrane of a neuron is
polarized
Individual postsynaptic potentials can combine to produce a larger potential in a process called
summation
Glial cells
support cells found in the nervous system
Mutations in the p53 gene prevent
suppression of the cell cycle
In mammals, circadian rhythms are coordinated by a group of neurons in the hypothalamus called the
suprachiasmatic nucleus (SCN)
The neurotransmitter diffuses across the
synaptic cleft and is received by the postsynaptic cell
Ribosomes are the sites of
translation
The steroid hormone receptors that bind to estrogens are
well-characterized
Define and explain summation.
when 2 EPSP/IPSPs occur quickly they can add together. postsynaptic potentials are graded, not all-or-nothing like action potentials. also get smaller with distance from synapse. can add EPSPs for a greater postsynaptic potential
Triploidy
when an organism has three copies of every chromosome instead of two (3n; 3 sets)
leukocyte
white blood cell