3_0 Unit 3

Contrast Eukaryotic genes with prokaryotic genes

Eukaryotic genes have introns prokaryotic genes do not. A Eukaryotic gene in a prokaryotic cell would not be able to synthesize proteins [express genes] because prokaryotic genes do not have introns and do not require splicing. Nor do they have spliceosomes. However a prokaryotic gene in a eukaryotic cell would be able to synthesize proteins.

What is the difference in sickle-cell hemoglobin?

Hemoglobin is a protein that is used to carry oxygen in blood. In sickle cell hemoglobin, the amino acid valine replaces the amino acid glutatamate.

What is the difference between the histones of heterochromatin & euchromatin?

Heterochromatin nucleosomes have histones with methyl groups on their tails; Euchromatin nucleosomes have acetyl (-COCH3 ) groups on their tails.

In what situation is CAP control of the lac Operon used?

If both glucose and lactose are present, bacteria prefers to breakdown glucose. When glucose is absent CAP turns on transcription of the lac Operon's structural genes.

What would cause certain daughter cells following meiosis II to be identical? What would cause them to not be identical?

If crossing over never took place...if crossing over did happened or independent assortment

Why did early investigators predict that there must be a reduction division in the sexual reproduction process?

If gametes(sex cells) contained the same number of cells as body cells(somatic), then the number of chromosomes would double with each new generation resulting in a completely new organism.

What happens when euchromatin genetically activates?

In a process commonly referred to as unpacking, a structure called "chromatin remodeling complex" pushes aside the histone portion of a nucleosome so DNA can be transcribed. Chromatin remodeling complex also functions in changing heterochromatin into euchromatin.

What happens to the haploid cells following meiosis?

In animals, haploid cells mature and develop into gametes(egg or sperm cells); In plants they become spores which becomes the haploid generation; the haploid generation then produces gametes which fuse to produce a diploid generation;

What is the fate of meiosis daughter cells?

In animals, the daughter cells become gametes that fuse during fertilization to become a diploid zygote; in plant cells, daughter haploid cells become spores that germinate and develop into a haploid generation;

How is meiosis 1 similar to and different from mitosis?

In both meiosis and mitosis DNA replication has previously occurred so each chromosome is made up of two sister chromatids. What's different is that in meiosis 1, 46 chromosomes align into two rows side by side as homologous pairs along the metaphase plate(synapsis). In mitosis, 46 chromosomes align into one row along the metaphase plate. Said another way in meiosis 1, 23 pairs of homologous chromosomes line up along the metaphase place. In mitosis, 46 chromosomes line up along the metaphase plate.

What are the functions of the chromatin remodeling complex?

In euchromatin it pushes aside the histones so DNA can be transcribed. This process is called DNA unpacking. The complex also affects gene expression by adding acetyl or methyl groups to histone tails.

reciprocal cross

In genetics, one of two crosses in which the opposite sexes are each coupled with two alleles for the same trait. This cross is usually used to determine if a genetic trait is linked to sex. For example, male of genotype A × female of genotype B (first cross). Then male of genotype B × female of genotype A (the reciprocal cross). Such crosses are used to detect sex linkage or maternal inheritance;

How are homologous chromosomes different in the normal stages of cell cycle compared to their status just before entering meiosis?

In normal stages of the cell cycle, there are 46 chromosomes. Just before entering meiosis chromosomes get duplicated(actually this happens in S stage). There are still 46 chromosomes but now each exist as a pair of daughter chromatids connected at its centromere.

Where is rRNA synthesized?

In the nucleolus.

Name and briefly describe the three stages of Translation

Initiation: step that brings all the translational componets[mRNA, tRNA & ribosomes] together. Elongation: protein synthesis step in which a polypeptide increases in length one amino acid at a time. Termination: final step in protein synthesis.

What does the wobble effect ensure will happen?

It helps ensure that despite changes in DNA base sequences, the correct sequence of amino acids will result in a protein.

What makes up a eukaryotic chromosome?

It is made up of a single DNA molecule and protein. The protein component is more than 50% of the chromosome. Some of these proteins function in DNA & RNA synthesis, but the majority help maintain chromosome structure [histones].

What disproves the concept of blended inheritance?

It was disproved by two major findings; (1) blending theory could not account for variations or species diversity found in future populations; if a population only yields intermediates, then eventually all future generations would come to a point where everything looks the same. In nature we don't see species that appear all the same. (2) the theory didn't explain how an intermediate offspring could regenerate parental traits in their offspring. In the example of the red & white flower cross, the pink offspring regenerated white and red offspring

What organisms are these likely to occur in and why?

Likely to occur in plants, because plants can self fertilize and meiotic failure only has to happen once, where as animals would need to separate organisms to undergo meiotic failure and then these daughter cells would need to meet with another 2n, and it would probably combine with a 1n gamete. If you ever get a triploid, you can't reproduce correctly with unaffected organisms. Plants will never create a triploid number of chromosomes.

How does meiosis bring about genetic variation?

Meiosis bring about genetic variation via recombination in two ways: crossing-over & independent assortment

What are the phases of meiosis?

Meiosis consist of two unique cell divisions, meiosis I & meiosis II. The phases of both meiosis I & II are prophase, metaphase, anaphase, and telophase.

Describe Mendel's experiment and results that led to the development of his Law of Independent Assortment

Mendel performed a dihybrid cross between true-breeding tall plants having green pods and short plants having yellow pods. As expected Mendel observed that the F1 individuals were all dominant in both traits. Mendel then predicted two possible outcomes for the F2 generation. If factors[genes] segregate independently, 4 different phenotypes [combinations] would be expressed. If factors[genes] do not segregate independently, only two phenotypes would be express. Mendel concluded the experiment and found four different phenotypes among the F2 generation. Based on this result, he formulated his 2nd law of heredity, Mendel's law of independent assortment.

Describe Mendel's experiment and results that led to the development of his law of segregation

Mendel preformed reciprocal crosses of short plants and tall plants; In both crosses, all the plants resembled tall parent. This result contradicted blended inheritance which predicted that all plants should be intermediate. Mendel then allowed the F1 plants to self-pollinate and found ¾ of the F2 generation were tall and ¼ were short a 3:1 ratio. From this result, he deduced that F1 plants were able to pass on a "factor" for shortness even though they themselves were not short; The results of his experiment led Mendel to develop his first law of inheritance; the law of segregation;

What is the main problem that happens in meiosis?

Non-disjunction: this problem will arise when sister chromatids are joined at centromere and homologues are joined during synapsis at chaismata...during anaphase this is supposed to be broken apart. Nondisjunction is the failure to pull apart sister chromatids during anaphase II or bivalents during anaphase I.

what is complete dominance?

One allele is able to be dominant enough to express a phenotype.

How does posttranscriptional control work?

Post transcriptional control works in one of two ways: (1) The pre-mRNA strand can be modified during processing; (2) The speed at which mRNA leaves the nucleus is altered. The first control mechanism[mRNA modification] is enacted via alternative RNA splicing. In alternative RNA splicing, multiple proteins are produced from the same mRNA strand. A spliceosome selectively cuts up a pre-mRNA strand by selecting to remove specific exons with introns. If an exon between introns also gets removed, the same sequence of mRNA will code for different proteins. Example of alternative splicing include the differences in hypothalamic and thyroid produced calcitonin. More examples include differences in neurotransmitters, muscle regulatory proteins & antibodies in other cells. As for the second posttranscriptional control mechanism [mRNA exit speed], not much is known about it. However, we do have evidence that indicates mRNA exits the nucleus at different speeds.

How are prokaryotic and eukaryotic chromosomes different?

Prokaryotic chromosomes have fewer proteins that complex with the DNA than eukaryotic chromosomes. Also the DNA and chromosomal structure is circular where eukaryotic chromosomes are linear.metastasis

** what is RNA and its function?

RNA stands for ribonucleic acid;(1) it participates in the translation of DNA's genetic code into the amino acid sequence for proteins(tRNA); (2) it serves as one of the components of ribosomes(rRNA) (3)it copies and carries the genetic code from DNA to the ribosome (mRNA);

Explain how the product & sum rule apply to a monohybrid cross of unattached (E) and attached (e) earlobes.

Since there are only two alleles for earlobes [attached & unattached] the chance of receiving either is ½ or 50%. If we want to know the chances of getting two or more specific events occurring together at once or a specific gene, we multiple the probability of the events occurring separately; Let's saw we want to know the chance of getting Ee... the chance of getting one E is ½ and the chance of getting e is 1/2 . so ½ × ½ = ¼. •

Contrast the genetic makeup of sister chromatids with that of non-sister chromatids

Sister chromatids come from the same parent and have genes that code the same trait and same allele . Non sister chromatids come from different parents code for the same trait but may different alleles.

What is the result of non-disjunction in Anaphase II?

Sister chromatids don't separate properly. 1 cell will have n+1 # of chromosomes, another will have n-1 and the other two cells will have the correct haploid number n...

snoRNA

Small nucleolar RNAs: a class of small RNA molecules that primarily guide chemical modifications of other RNAs, mainly ribosomal RNAs, transfer RNAs and small nuclear RNAs.

What happens during the second stage of translation?

The 2nd step in translation is elongation. With a tRNA molecule already at the P site, elongation begins when another tRNA-amino acid complex arrives and binds at the A site. A protein called elongation factors facilitates the binding[between mRNA codon & tRNA anticodon.. Next, a peptide bond is formed between the two amino acids. This bond is catalyzed by ribozymes. Finally, the ribosome moves to the next codon of mRNA shifting the A site tRNA into the P site, and the P site tRNA to the E-site. At this point the A site is empty, & ready to receive the next tRNA carrying amino acid. The E site tRNA then leaves the ribosome. This process repeats itself until the ribosome reaches a stop codon.

What happens during the first stage of translation?

The first stage is initiation. The following events occur: (1)the small ribosomal subunit binds to mRNA at the G-cap; (2) the first tRNA molecule then binds to mRNA at codon AUG. [the first tRNA molecule is commonly referred to as "the initiatior tRNA" and is the same for all polypeptides. Binding between tRNA & mRNA happens at the ribosomes P site [not the A site].(3) the large ribosomal subunit attaches on top.

What happens during the third stage of translation?

The last stage of translation is termination; The ribosome comes to a stop codon on mRNA. A release protein factor then binds to the stop codon and cleaves(via hydrolysis) the polypeptide from the last tRNA in the P site. The tRNA and polypeptide leave the ribosome, which then dissociates into its two subunits.

What is the exception/condition to the law of independent assortment?

The law of independent assortment only applies when the alleles for the two different traits are on different chromosomes. If they are on the same chromosome, then the dihybrid crosses [remember this is the second cross of two pure-breeds] will only express two phenotypes instead of the four. We call alleles for different traits on the same chromosome linked genes.

What regulates whether a specific segment of chromatin is in its genetically active form [euchromatin] or genetically inactive form [heterochromatin]?

The proteins that complex with DNA, histones, have amino acid "tails" on them. In heterochromatin these tails have methyl groups. In euchromatin the tails have acetyl groups. A structure called the "chromatin remodeling complex" puts acetyl groups on heterochromatin, changing it to euchromatin.

How does translational control work?

There are three different mechanisms for translational control. These mechanisms also affect the mRNA strand, but unlike posttranscriptional control they occur in the cytoplasm. Specifically, sometime after the mRNA has reached the cytoplasm but before the protein is synthesized. [1]The first mechanism involves cytoplasmic activities that remove the 5' G cap. If the cap is removed translation may not happen &/or the mRNA may be destroyed. If the G cap is left alone, translation occurs. [2] In the next mechanism, cytoplasmic activities that remove or affect the length of the 3' poly-A tail also function to regulate gene expression. If the poly-A tail is shortened the mRNA strand time in the cytoplasm is also shortened. This results in differential protein expression because the ribosome will synthesize a smaller than expected protein. If the poly-A tail is left alone a longer protein is produced. However If the poly-A tail is completely removed, the mRNA may be destroyed and no protein produced. [3] The third mechanism involves the use of microRNA (miRNA). microRNA regulate genetic translation by binding to mRNA[which forms a double-stranded RNA complex] & either inhibiting or destroying it. This also results in no protein synthesis.

Explain why traits controlled by polygenes show continuous variation and produce a bell shaped curve?

This is due to all of the possible and different genotypes that can be produced.

Genetic code is universal. What does this mean and why is it important?

This means that all living things use the same code between its DNA & subsequent proteins with a few exceptions. The genetic code found in mammalian mitochondria & chloroplast differ slightly and are the exceptions. The universal nature of the genetic code provides strong evidence that all living things share a common evolutionary heritage.

Explain the concept of multiple alleles

To this point in our discussion, we have only seen two alleles for a trait, a dominant allele (ex. Tall fingers) & a recessive allele (ex. Short fingers). Most traits are not limited to only two allelic versions. They can have multiple versions of trait. This is referred to as multiple alleles. The quintessential example of this is blood type. Blood has a total of four alleles. Two dominant alleles (type A & type B), one recessive allele (type O) & allele type AB blood which is an example of codominance.

What is the central dogma of molecular biology?

Transcription and translation proceed together. Said another way genetic information flows from DNA to RNA to proteins.

Describe the events that take place during transcription

Transcription begins when RNA polymerase attaches to a promoter site on the template strand of DNA. Next, RNA polymerase moves along the template strand joining RNA nucleotides complementary to the DNA nucleotides of the coding strand. RNA polymerase is only capable of synthesizing mRNA in the 5' to 3' direction. Therefore, it adds nucleotides to the 3' end of the template strand. This process continues until RNA polymerase reaches a stop sequence which causes RNA polymerase to stop transcribing DNA and release the pre-mRNA molecule which is now called an mRNA transcript or pre-mRNA.

What will transcription produce?

Transcription results in a pre-mRNA/ primary mRNA transcript...modifications must occur before the mRNA can leave the nucleus

How does transcriptional control work?

Transcriptional control is achieved when the mechanism utilizes transcription factors and either an activator or a repressor. The control mechanisms works in the following way: [i] a group of transcription factors bind to a promoter just adjacent to a gene. [ii] It then attracts and helps RNA polymerase bind. [iii]transcription activators bind to DNA at a region called an enhancer. [iv] a hairpin loop forms in DNA to bring the activator attached enhancer into contact with the promoter. Mediator proteins act as a bridge between transcription factor & activator which then causes transcription to occur quickly; This same process happens when transcription is turned off with the exception that repressors bind to silencers instead of activators to enhancers.

Where do triploids come from?

Triploids form when the spindle apparatus does not form correctly and the 4 gametes consist of two diploid gamete cells and the other 2 having zero chromosomes...the 2n gametes combine via fertilization with a regular haploid gamete to form a 3n individual.

What's the difference between triploidy and trisomy?

Triploidy is when the entire organisms set of chromosomes has an extra chromosome. this produce as 3n individual. In trisomy, only one of the homologous pairs has an extra chromosome.

True or False || abnormal numbers of sex chromosomes are less problematic than abnormal number of autosomes.

True

True or False Chromosomes are duplicated before Meiosis I

True. the 46 parent chromosomes in humans are duplicated into sister chromatids during the S phase of the cell cycle.

*Great apes have 24 haploid chromosomes, while humans have 23 haploid chromosomes...why?

Two chromosomes that were separate probably became fused. it was discovered that chromosome 2 has a fusion point indicating common ancestory between human and great apes...Fusion is a way of reducing the chromosome number, producing an organism that is viable, but possibly not fertile....jumping genes could have caused this or crossing over happened

How was it determined that a codon is a sequence of 3 bases?

Well it was know that there are 20 amino acids. 4 bases could only result in 16 codons, so not enough . 3 base codons result in at least 64 codons leaving enough for 20 amino acids.

What three major modifications occur during mRNA processing?

[1] A G'cap or modified guanine nucleotide (aka GTP) is added to the 5' top [head] of the mrNA transcript. It tells the ribosome where to attach to begin translation. (2) on the 3' end[tail] a chain of adenine nucleotides is added. This chain is called the poly-A tail and can contain anywhere from 30-200 nucleotides of adenine...its functions include helping the mRNA strand exit the nucleus and it determine how long mRNA can exist in the cytoplasm before being broken down by hydrolytic enzymes. The longer the poly-A tail the longer the mRNA exist in the nucleus without being degraded. This function is often likened to a fuse of a firecracker or bomb. (3) Lastly, non-coding segments(introns) within the mRNA are removed by spliceosomes.

What three enzymes are synthesized by the lac Operon to catabolize/breakdown] lactose?

[1] beta-galacatosidase: enzyme that catabolizes lactose into monomers glucose and galactose; [2] permease: enzyme that allows lactose to enter the cell; [3] transacetylase: enzyme with accessory function in lactose metabolism;

nucleosome

a basic unit of DNA packaging in eukaryotic cells, consisting of DNA wound around a histone; For the 2 meter long DNA found in eukaryotic chromosomes, a total of 8 histones [nucleosomes] are used to wrap it. The 8 DNA wrapped histones appear as a "string of beads." Each bead is a nucleosome;

anueoploidy

a change in the chromosome number resulting from nondisjunction during meiosis;

(chromosomal structure) translocation

a chromosomal segment is removed from one chromosome and inserted into another non-homologous chromosome; in Down syndrome 5% of cases are due to translocation between chromosome 21 & 14.

Polyribosome

a complex of multiple ribosomes where a single strand of mRNA passes through multiple ribosomes

punnett square

a diagram that is used to predict an outcome of a particular cross or breeding experiment.

*cyclins

a family of internal signaling proteins produced during phases of the cell cycle; the amount of cyclin present in the cell will either increase or decrease as the cell cycle continues; specific cyclin must be present for the cell to proceed from G1 to S and from G2 to M.

operon

a functional unit of genomic DNA containing a cluster of genes under the control of a single regulatory signal[or gene]. An operon typically includes a promoter, operator, structural genes & the regulatory signal.

regulator gene:

a gene located outside of the operon that will code for a protein[repressor protein] that controls whether the operon is active or inactivce.

monohybrid cross

a genetic cross of the F1 generation after allowing true-breeding individuals to cross a single trait with two alleles; [the book states that a monohybrid cross is ALWAYS between two true breeding(homozygous genotype) organisms; Also these offspring will self-pollinate and cross again producing an F2]

anticodon

a grouping of three RNA nucleotide bases that are the complementary pairs to a specific mRNA codon.

incomplete Dominance

a heterozygote trait where the proteins of the dominant allele is not at full strength and result in an intermediate phenotype being expressed Said another way, the dominant allele only partially dominates expression of its partner(the recessive allele). The quintessential example of this is the cross between red & white flowers to produce pink intermediates. Incomplete dominance is not an example of blended inheritance because when you allow this population (pink flowers) to self-pollinate, parental phenotypes (red & white flowers) reappear.

Explain how lampbrush chromosomes in vertebrate euchromatin is genetically active?

a lampbrush chromosome is genetically active because it has had its histone pushed aside by the chromatin remodeling complex so that its DNA is unwound into large loops that can easily be accesed by RNA polymerase.

test cross

a method used to determine if an individual with a dominant phenotype is homozygous dominate or heterozygous for a particular trait. In the test cross the dominant individual is breed with a recessive individual.

(chromosomal structure) deletions

a mutation where the end of a chromosome breaks off or two simultaneous breaks lead to the loss of an internal segment

enhancer

a region of DNA, that transcription activators bind to in order to speed up transcription. Enhancers often are far away from the promoter site;

* nucleoid

a region that contains the single circular DNA molecule of bacteria. It is usually coiled on a chromosome;

(chromosomal structure)inversion

a segment of a chromosome is turned around 180 degrees;. The position and sequence of the genes are altered

gene

a segment on homologous chromosomes(Tait says on one chromosome) that codes for a specific trait(red hair)

RNA primer

a sequence of RNA nucleotides that serves as a starting point for DNA synthesis. It is required because the enzyme that catalyzes synthesis, DNA polymerase, can only add new nucleotides to an existing strand of DNA.

codon

a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule;

operator

a short segment of DNA that is the location where an active repressor binds to prevent RNA polymerase from attaching to the promoter. This action prevents transcription.

**promoter

a short segment of DNA, usually occurring upstream from a gene's coding region, where RNA polymerase first attaches when a gene is to be transcribed. the promoter acts as a control site in the expression of the gene.

promoter

a short segment of DNA, usually occurring upstream from a gene's coding region, where RNA polymerase first attaches when a gene is to be transcribed. the promoter acts as a control site in the expression of the gene.

Briefly describe tRNA and its function...

a single strand of RNA folded into a cloverleaf(it looks plus shaped to me). The cloverleaf shape is held together by hydrogen bonding between nucleotides. amino acids bind to the 3'end forming what is called an "amino acid-tRNA complex." This complex then travels to the ribosome to deliver its amino acid to the developing polypeptide.

corepressor

a substance that activates a repressor protein by causing it to bind to the operator and stop transcription. In the trp Operon, tryptophan is the corepressor;

one-trait testcross

a test cross used to determine if an individual with the dominant phenotype is homozygous dominant or heterozygous. If the individual is homozygous dominant, all offspring will be the same.

meiosis

a type of nuclear division that reduces the chromosome number from diploid(2n) to haploid(n). Unlike mitosis, it involves two rounds of nuclear division and produces four daughter cells with half the total number of chromosomes as there were in the diploid parent nucleus. Daughter cells are not genetically identical to the parent cells or to each other;

karyotype

a visual display of chromosomes arranged by shape, size & banding pattern.

microRNA

abbreviated miRNA: microRNA are small processed pieces of introns that combine with protein to form a complex called the RNA-induced silencing complex[RISC] This complex targets specific mRNA molecules, complementary base pairs with them[ forming a double-stranded RNA complex] and then destroys or inhibits it from being translated by the ribosomes.

*bivalent

also called a tetrad; two homologous chromosomes that undergo synapsis and stay in close association during the first two phases of meiosis 1;

bivalent:

also called a tetrad; two homologous chromosomes that undergo synapsis and stay in close association during the first two phases of meiosis 1;

homologous chromosomes

also called homologues; a pairing of chromosomes, one of paternal origin, the other of maternal origin that pair up with each other during meiosis; they contain genes that code for the same trait, although the genes may code for different variations of that trait;

somatic cells

also known as body cells; any cell in the body that is not a sex cell(or gamete) and has a full (diploid 2n) number of chromosomes;

* alleles

alternate forms of the same gene;(ex: a gene that codes for short fingers and a gene that codes for long fingers are alleles)

alleles

alternate forms of the same gene;(ex: a gene that codes for short fingers and a gene that codes for long fingers are alleles)

A site

amino site: one of three tRNA binding sites in a ribosome; During initiation, the A site is empty. During elongation the A site receives new tRNA carrying amino acid one at a time.

repressible operon

an active operon that gets turned off when a repressor protein binds to its operator. Said another way, repressible operons are operons that go from on to off. They are usually involved in anabolic pathways.

recessive allele

an allele that expresses its effect only in the homozygous state; its expression is masked by a dominant allele; it is represented by a lowercase letter

RNA Polymerase

an enzyme that is responsible for making mRNA from DNA. It is only capable of synthesizing mRNA by joining nucleotides in the 5' to 3' direction. The means the resulting mRNA strand will be 5' to 3'.

range of dominance

an individual with a single allele for a trait will produce less of the protein that causes that trait than an individual with 2 alleles.

wobble hypothesis

an observation that a single tRNA can bond with more than one codon. Said another way, the genetic code contains 64 codons( actually there are only 61 codons because 3 are stop codons). We would therefore expect to also see 64 tRNA anticodons. However this is not the case. There are fewer tRNA anticodons than expected because tRNA's can pair with more than one codon. the hypothesis specifically states that the first two codons obey the RNA complementary base pairing rules. However, the third position may vary.

Alternation of generation

an organism that has both haploid and diploid phases of their life cycle;

inducer

any substance that binds to a repressor protein[deactivating it] thus causing the repressor to be removed from the operator. Removal of the repressor allows RNA polymerase to bind to the promoter and transcribe the gene.

What is the result of non-disjunction in Anaphase I?

bivalents don't separate properly. Of the four daughter cells, two cells will be n+1 number of chromosomes and two cells will have n-1 number of chromosomes... When primary non disjunction happens there are no normal gametes that form

CAP

catabolite activator protein: a protein that activates transcription of a catabolic operon's structural genes when glucose is not available for catabolism. CAP does this by binding to DNA and exposing the promoter site to RNA polymerase;

chromosomal mutations

changes in chromosome number or structure;

autosomes

chromosomes that do not code for an organism's sex; In humans we have 23 homologous pairs or 46 chromosomes; 22( or 44) are autosomal because they code for all traits except sex.

spliceosomes

complexes made of proteins called snrnp(small nuclear ribonuclear proteins) [pronounced SNURPS] Spliceosomes cut up pre-mRNA so that all non-coding portions of the mRNA strand are removed. Said another way, spliceosomes deletes introns and connect the exons that remain.

Describe the prokaryotic chromosome...

composed of DNA and associated proteins but much less protein than eukaryotic chromosomes; the chromosome is a circular loop attached to the inside of the plasma membrane;

negative control [gene regulation]

control of gene regulation that involves the use of a repressor that turns that either activates or deactivates the operon.

positive control [gene regulation]

control that involves the use of an activator protein to turn transcription[or operon possibly on]

Telophase II and cytokinesis

daughter cells begin to form; a nuclear envelope forms around each set of chromosomes & cytokinesis takes place. Cytokinesis results in the production of daughter cells; at the end of telophase and cytokinesis there are four daughter cells.

**Synapsis

during meiosis 1, chromosomes that are homologues migrate towards each other and line up side-by-side;

*Synapsis

during meiosis 1, chromosomes that are homologues migrate towards each other and line up side-by-side;

Synapsis

during meiosis 1, chromosomes that are homologues migrate towards each other and line up side-by-side;

Telophase I

during telophase I, daughter cells are starting to form; completion of telophase I is not necessary during meiosis. When it does occur, the nuclear envelope reforms, nucleoli reappear and the mitotic spindle disappears. This phase may or may not be accompanied by cytokinesis;

ribozymes

enzymes made of RNA instead of proteins. They function in intron removal and protein synthesis(specifically the connection of one amino acid to another).

Compare the processes of Meiosis II to Mitosis

events of Meiosis II are the same as mitosis, except the nucleus contains a haploid number of chromosomes instead of a diploid.

E site:

exit site: is the site where used up tRNA leaves the ribosome;

Poly-X

females that have three or more X chromosomes;

Turner syndrome

females that only have one sex chromosome; XO; ovaries of Turner females never become functional;

Where do gamete chromosomes come from?

gametes have only one chromosome of each kind derived from the paternal or maternal homologue.

genomic imprinting

gene expression that depends on whether the chromosome carrying the gene is inherited from the mother or the father; Methylation of DNA accounts for genomic imprinting because an inherited gene that has been methylated does not get expressed. Only the gene coming from the parent without methylation is expressed for a specific trait.

structural genes

gene or genes in the operon that code for the enzymes needed in a specific metabolic pathway.

X-linked inheritance

genes that have nothing to do with gender assignment, but are carried on the X chromosome. X-lined alleles have a different pattern of inheritance than alleles that are on the autosomes because the Y chromosome is lacking for these alleles and the inheritance of a Y chromosome cannot offset an X-linked recessive trait. As a result, sex linked recessive traits appear more frequently in males than females.

heterozygous

genotype that possess one of each allele for a particular trait;

homozygous dominant

genotype that possess two dominant alleles for a trait;

proteasomes

giant protein complexes that degrade or destroy proteins so they are no longer active;

haploid

half the total number of chromosomes of an organism; (n)

If the inheritance pattern for a genetic disorder was exemplified by incomplete dominance, what would be the genotype?

heterozygous

carrier

heterozygous individual who does may or may not exhibit traits of the disease, but are able to pass on an allele for a recessively-inherited genetic disorder;

histones

highly alkaline proteins found in eukaryotic cells that package and order DNA into structural units called nucleosomes; they do so by acting as a spool around which DNA winds; histones also provide the chromosome with structural support.; there are 5 different types of histones;

*histones

highly alkaline proteins found in eukaryotic cells that package and order DNA into structural units called nucleosomes; they do so by acting as a spool around which DNA winds; histones also provide the chromosome with structural support; there are 5 different types of histones;

Why are meiosis and sexual reproduction important in responding to changing environments?

identical copies of a duplicated chromosome that have not been pulled apart and are connected at their centers(the centromere)

sister chromatids

identical copies of a duplicated chromosome that have not been pulled apart and are connected at their centers(the centromere)

What are the functions of introns?

it allows a cell to pick and choose which exons will go into a particular mRNA strand, or what exons to cut out with introns...Introns also help in crossing over during meiosis...crossing over happens at intros locations. Even if crossing over is not perfect it will not affect the gene because it has some room for error.

How does interkinesis differ from interphase?

it differs in that interkinesis has no DNA replication phase

law of segregation

it states that (1)each individual has two factors for each trait; (2) the factors segregate during the formation of gametes (3)Each gamete contains only one factor from each pair of factors. (4) fertilization gives each new individual two factors for each trait. This law is explained by what happens during meiosis II.

Compare the functions of mRNA, tRNA, and rRNA during gene expression.

mRNA function is in transcription. It makes a copy of the DNA sequence that will code for a particular protein. tRNA is part of translation. It has the responsibility of retrieving the specific amino acids that will be part of the proteins and brings them to the ribosome. rRNA is a component of the ribosome that functions to make the protein by catalyzing the formation of peptide bonds.

What are the three major classes of RNA?

mRNA: messenger RNA: copies the genetic code from DNA and carries it to the ribosomes in the cytoplasm; tRNA(transfer RNA) transports amino acids to the ribosomes. rRNA: ribosomal RNA rRNA and protein makes up ribosomes where proteins are synthesized;

Klinefelter syndrome

males that have one Y chromosome and two or more X chromosomes; •

Jacobs syndrome

males with two Y chromosomes instead of one; results from nondisjunction during spermatogenesis;

mendel's particulates of inheritance;

mendel believed that minute(very small) particles (what we now call genes) contain the information of inheritance. He believed that inheritance involved the reshuffling of these particles from one generation to the next.

proteomics

new field of biology that aims to understand protein structures and the functions of metabolic pathways.

intron:

non-coding segment of mRNA that get removed by spliceosomes before the mRNA leaves the nucleus;

primary nondisjunction

nondisjunction that happens during meiosis I; both members of a homologous pair go into the same gamete; when primary nondisjunction happens, there are no normal gametes produced.

secondary nondisjunction

nondisjunction that happens during meiosis II; sister chromatids fail to separate and both daughter chromosomes go into the same daughter cell. When secondary nondisjunction happens there will be two normal gametes and two aneuploid gametes;

multifactorial (inheritance) traits

norm of reaction): traits that are affected by multiple genes( polygenes) ; the book give eye color an skin color as examples of polygenic traits;

epistasis

one gene that overrides another gene, where the two genes are located on different chromosomes.

Why does the zygote have pairs of each kind?

one member of a homologous chromosome was inherited from the male parent and the other was inherited from the female parent by way of the gametes.

translational control

one of five eukaryotic mechanisms for controlling genetic expression[in the cytoplasm] that controls when translation begins and how long it continues; Any changes to the 5' G cap or the 3' poly A tail can affect the length of translation; It has recently been discovered that introns[using microRNA] may also be involved in affecting the life span of mRNA; translational control is one of two processes that occurs in the cytoplasm;

posttranslational control

one of five eukaryotic mechanisms for controlling genetic expression[in the cytoplasm] that involves additional changes to the synthesized protein before it becomes biologically functional.

posttranscriptional control

one of five eukaryotic mechanisms for controlling genetic expression[in the nucleus] that involves changes in mRNA processing or mRNA exit speed. In other words, post transcriptional control involves differential mRNA processing or changes in the speed at which a mature [processed] mRNA leaves the nucleus.

transcriptional control

one of five eukaryotic mechanisms for controlling genetic expression[in the nucleus] that stimulates or stifles transcription.Of the five mechanism for gene regulation, this one is most critical. Transcription factors, activators, repressors, & transposons are the "instruments" of transcriptional control.

chromatin structure [genetic regulation]

one of five eukaryotic mechanisms for controlling genetic expression[in the nucleus]. Mechanism uses variations in chromatin structure to control when transcription occurs. If genes are not accessible to RNA polymerase, they cannot be transcribed. Highly condensed chromatin cannot be transcribed because RNA polymerase cannot attach to DNA. However, loosely condensed chromatin can be transcribed because RNA polymerase attaches easily.

phenotype

physical appearance of the expressed trait.

How does posttranslational control work?

posttranslational control is the last chance a cell has to control genetic expression. It happens after a protein has been synthesized & before or after it has been activated. There are two main mechanisms for posttranslational control. [1] The first means of control includes cleaving or folding of the protein to activate or deactivate it. For example, bovine insulin is activated when a 30 amino acid sequence is removed (cleaved). [2] The second mechanism involves destroying [or degrading] the protein after it has been activated to prevent it from continuing to be expressed (in other words, to stop the protein from continuing to perform its function). For example, proteasomes are used to destroy [degrade] cyclins to stop them from functioning in the cell cycle.

sexual reproduction

process that creates a new organism by combining the genetic material of two organisms;

translation

process where mRNA directs the sequence of amino acids in polypeptide formation; it is the 2nd & final stage of gene expression. It takes place in the cytoplasm

translation

process where mRNA directs the sequence of amino acids in polypeptide formation; it is the 2nd & final stage of gene expression. It takes place in the cytoplasm.

*chiasmata

regions where non-sister chromatids are attached and exchange parts due to crossing over;

chiasmata

regions where non-sister chromatids are attached and exchange parts due to crossing over;

asexual reproduction

reproduction in which the offspring are genetically identical to the parent; this type of reproduction is common of unicellular organisms;

spores

reproductive cells that develop into a new multicellular structure without the need to fuse with another reproductive cell;

What joins one amino acid to another amino acid, in protein synthesis?

ribozymes

exons

segments of mRNA/DNA that are part of the genetic code for a protein.

snRNA

small nuclear RNA: RNA used by the spliceosome to identify location of introns

What role does snRNA play in the nucleus and snoRNA serve in the nucleolus?

snRNAs are used by the splicosome to identify introns that need to be removed...snoRNAs helps process rRNA and tRNA molecules

telomeres

special nucleotide sequences found at the end of eukaryotic DNA that don't code for proteins; usually they are repeats of short nucleotide sequences;

P site

stands for peptide site; one of three tRNA binding sites of a ribosome; during initiation the first tRNA molecule [containing amino acid methionine] binds here instead of the A site; At the start of elongation, the A and P site both have amino-tRNAs in their slots. During elongation, the A site tRNA moves to the P site which pushes its tRNA to the E site.

template strand

strand of DNA that containing the gene(s) of interest.

noncoding strand

strand of DNA that does not get copied into mRNA.

coding strand

strand of RNA that gets synthesized and become mRNA.

antiparallel

term that means the strands of DNA are arranged in opposite directions;

epigenetic inheritance

term used to describe inheritance patterns that do not depend on the genes themselves. Said another way, epigenetic inheritance are changes in genetic expression [or phenotype] that are caused by mechanisms not found in the DNA genes. For example, a structure called "chromatin remodeling complex" has the ability to add methyl or acetyl groups to histones. If when adding a methyl group to a histone, it also adds one to DNA, the DNA becomes inactive. This is a specific example of epigenetic inheritance called genomic imprinting;

semiconservative replication

term used to describe replication of DNA where each strand of the original DNA double helix serves as a template for a new daughter DNA molecule.

two-trait testcross

test-cross used to determine if the individual showing two dominant characteristics are homozygous dominant for both, heterozygous for both, or homozygous dominant for one trait and heterozygous for the other. (1)If an organism is homozygous dominant for both, only one type of gamete will form; (2)if the organism is heterozygous for both traits four different phenotypes will be expressed. (3)If the organism is homozygous for one trait and heterozygous for the other only two phenotypes will be expressed.

Barr body

the X chromosome that becomes an inactive mass in males and females with an extra X;

zygote

the cell that forms when gametes fuse; zygote has a full (diploid 2n) number of chromosomes;

Anaphase II

the centromeres separate, and the two non-identical sister chromatids of each chromosome move to opposite poles. The separated chromatids are now called (daughter) chromosomes in their own right;

product rule of probability

the chance of two or more independent events occur together is the product of the probability of the events occurring separately;

euploidy

the correct number of chromosomes in a species;

*crossing over

the exchange of genetic material between non-sister chromatids of a bivalent during meiosis I. this process is a method genetic recombination used to create genetic variation; after the non-sister chromatids exchange parts, they are no longer genetically identical. Therefore the offspring will have a different set of alleles than their parents.

crossing over

the exchange of genetic material between non-sister chromatids of a bivalent during meiosis I. this process is one genetic recombination method for creating genetic variation; after the non-sister chromatids exchange parts, they are no longer genetically identical to each other or the original chromosome. Therefore the offspring will have a different set of alleles, than their parents.

nondisjunction

the failure of chromosomes to separate at meiosis or mitosis;

*transcription

the first step in gene expression; process where a DNA strand serves as a template for mRNA synthesis;

transcription

the first step in gene expression; process where a DNA strand serves as a template for the synthesis of mRNA;

Metaphase I

the following events happen during this phase: (1) bivalents(homologues) held together by chiasmata move towards each other and then align themselves on the metaphase plate; bivalents align themselves independently(meaning the orientation of one bivalent is not dependent upon the orientation of others (2) mitotic spindle is now fully formed;

Anaphase I

the following happens during Anaphase I: (1)the homologues of each bivalent separate and move towards opposite poles; with that said the non-identical sister chromatids do not separate(like the would during mitosis). Each chromosome still has two chromatids

Metaphase II

the following occurs during metaphase II: (1)the haploid number of chromosomes align at the metaphase plate; in humans, 23 chromosomes align at the metaphase plate; (2) spindle apparatus formation completes; (3) for each chromosome, the kinetochore of the non-identical sister chromatids face opposite poles; each is attached to a kinetochore microtubule coming from that pole

Prophase II

the following occurs during prophase II: nuclear envelope breaks down, and the spindle apparatus starts to form; centrosomes duplicate;

Prophase I

the following processes take place during prophase I: (1) nucleolus disappears, (2)nuclear envelope fragments; (3) chromatin condense into chromosomes and become visible (4) centrosomes migrate away from each other (5) spindle apparatus starts to form; (6) homologous chromosomes, each consisting of two chromatids, undergo synapsis to form bivalents; (6) crossing over of non-sister chromatids occur resulting in (sister) chromatids that are no longer identical;

What is alternative RNA splicing?

the idea that multiple proteins can be produced from the same mRNA strand... this functionality is created when the spliceosome selectively cuts up a pre-mRNA strand.. Lets say that a certain mRNA transcript contains 5 exons and 6 introns that alternate. Normally, we would expect the spliceosome to cut out all the introns leaving an mRNA strand made of all 5 exons. However, mRNA does not have to have all its exons in a single strand of mRNA. With alternative RNA splicing, the splicesome cuts the primary mRNA strand so that we can have have two mRNA strands, one containing 2 exons and the other containing 3.

An Interesting fact about red blood cells

the main function of red blood cells is to transport oxygen through-out the body. Red blood cells use the protein hemoglobin to carry oxygen. The interesting fact about red blood cells is that they eject their nucleus, along with its DNA. How are red blood cells able to replenish its supply of hemoglobin if it no longer contain hemoglobin's genetic code? The poly-A tail on the hemoglobin mRNA strand is very long which allows it to remain in the cytoplasm for a long period of time before it is degraded. In fact hemoglobin, can be synthesized for several months in red blood cells. This happens to coincide with how long a red blood cells lives. Once this time has passed, the cell is no longer functional and is then replaced by new red bloods cells.

Trisomy 21

the most common autosomal trisomy seen in humans; it is also called Down syndrome; it occurs when three copies of chromosome 21 are present and is caused by nondisjunction.

Interkinesis

the period between meiosis I & meiosis II. It is similar to interphase between mitotic divisions except DNA replication does not occur;

(chromosomal structure) duplication

the presence of a chromosomal segment more than once on the same chromosome; (1) often this manifest in a broken segment of from one chromosome attaches to its homologue or unequal crossing over may occur;

genetic recombination

the process of forming new allelic combinations in offspring either naturally, by crossing over or independent assortment.

DNA unpacking

the process where the chromatin remodeling complex pushes aside the histone portion of a nucleosome so that DNA polymerase can attach to the DNA promoter and transcription can begin.

gamete

the reproductive cell of an organism which will undergo sexual reproduction. Gametes have a haploid number of chromosomes; if the gamete contained the same number as body cells, the number of chromosomes would double with each new generation(creating a new species each time); egg & sperm cells are gametes;

dihybrid cross

the second generation self-fertilization cross of heterozygous organisms after the initial cross between true-breeding plants that differ in two traits;

genetic code

the set of rules by which information encoded within genetic material (DNA or mRNA sequences) is translated into proteins by living cells. it consists of 64 triplets of nucleotides which each encode for a specific amino acid(of the 20);

gene locus

the specific location of alleles(genes) on a homologous chromosome.

diploid

the total number of chromosomes of an organism; (2n)

replication fork

the two V-shaped ends of the replication bubble where DNA is replicated;

genotype

the two alleles that make up a gene/genetic code for a trait.

At the beginning of meiosis 2, describe the state of the two daughter cells

the two daughter cells do not have a full number of chromosomes (diploid 2n). They have the haploid (n) number. Said another way, they have one chromosome from each pair of homologues. In humans, these daughter cells would contain 23 chromosomes; with each chromosome still consisting of two non-identical sister chromatids.

concept of blended inheritance

theory that an offspring's genetic makeup is an intermediate of its parents; For example, a cross between red & white flower plants would produce offspring that are pink. theory about trait inheritance that was believed to be true until late nineteenth century;

Mendel's law of independent assortment

there are two parts two this law:(1) each pair of factors segregates independently of one another [by pair of factors we mean pairs of genes that code for different things. For example one pair of genes codes for [hair length] and another pair of genes codes for [eye color]). Said another way Mendel's Law of Independent Assortment says that the way one pair of factors [homologous chromosomes] segregates [aligns on the metaphase plate during meiosis I] does not affect how another pair of factors segregate. (2) All possible combinations of factors (genes expressed as traits) can occur in the gametes. Said another way, Because the homologous chromosome pairs of an individual can line up on the metaphase plate however they want, the resulting gametes will be unique. The gamete cell have any of the possible arrangements of factors....the law of independent assortment is evidenced by what happens during meiosis 1.

what role do the first few amino acids in a polypeptide serve?

they act as a signal peptide that indicates where the polypeptide belongs in the cell or if it is to be secreted.

*chromatin

threadlike material made up of DNA, and protein; chromatin is the uncondensed & uncoiled version of chromosomes; under a microscope chromatin appears threadlike or grainy; chromatin is located in the nucleoplasm of the nucleus

autosomal dominant

when a genetic disorder is autosomal dominant, the normal allele is recessive(a) and an individual with the alleles AA or Aa has the disorder;

autosomal recessive

when a genetic disorder is autosomal recessive, the normal allele (A) is dominant and only the individuals with the alleles aa have the disorder;

pleiotropy

when a single gene (allele) affects more than one trait. For example the allele for pigment can control hair color, eye color, and skin color) Marfan syndrome is an example due to a mutated gene on chromosome 15. When a gene on chromosome 15 is affected an individual may have longer extremities, a weakened aorta, and poor eyesight.

codominance

when more than one dominant gene is expressed

polygenic inheritance

when one trait is affected by two or more genes (Tait says alleles instead of genes; book says sets of alleles); Since more genes effect the trait, we expect more variations in the phenotypic expression. For example, if seven genes effect height, we may be able to deduce that tallest would be the dominant phenotypes of each gene, the smallest height could be caused by all 7 being receive, all 7 heterozygous could correspond to intermediate, and all in between caused by variation of dominant , recessive & heterozygous.

incomplete penetrance

when the dominant allele does not express the dominant phenotype or when the dominant allele does not completely express the dominant phenotype.

sum law of probability

when the same event occurs in more than one way, you can add the results.

Describe how crossing over happens

(1) At synapsis, homologues line up side by side and a nucleoprotein lattice forms between. This lattice functions to hold the bivalent together; (2) Crossing over takes place (meaning non-sister chromatids of the homologous chromosomes exchange parts) (3) the nucleoprotein lattice breaks down. Homologues are temporarily held together by chaismata. (4)[not part of crossing over but happens next] during anaphase 1 the homologues separate and are distributed to daughter cells.

what are the characteristics of an autosomal dominant disorder?

(1) affected children always have an affected parent; (2) Carriers are affected phenotypically; (3) Two affected parents can produce an unaffected child (4) two unaffected parents will not have affected children (5) males and females are affected with equal frequency

DNA helicase

(1) an enzyme that catalyzes the energy-dependent unwinding of the DNA double helix during DNA replication. (2) a class of enzymes that function to unwind DNA. They are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands using energy derived from ATP hydrolysis.

DNA ligase

(1) an enzyme that joins up breaks or fragments in a single strand of DNA (2) a specific enzyme, a ligase, that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.

what are the characteristics of an autosomal recessive disorder?

(1) most affected children will have normal parents; (2) Carriers are unaffected phenotypically; (3) Two affected parents will always have affected children (4) close relative who reproduce are more likely to have affected children[are we talking about incest here] (5) males and females are affected with equal frequency

What three important properties were discovered by scientists about the genetic code?

(1) the genetic code is degenerate(meaning that most amino acids have more than one codon; there are 64 triplets(actual 61. Three are stop colons) that code for 20 amino acids; this protects against harmful mutations; (2) the genetic code is unambiguous in that each triplet codon codes for only one amino acid. Said another way a single codon doesn't code for two different amino acids; (3) the codes have start and stop signals; there is only one start signal, and three stop codons;

What are the two major steps in gene expression?

(1) transcription (2) translation;

Compare the processes of Meiosis I to Mitosis

(1)Before both meiosis 1 and mitosis, DNA is replicated only once; (2)During prophase I of meiosis, homologues pair and undergo crossing over; this does not happen in mitosis; (3) during metaphase I of meiosis, bivalents align at the metaphase plate; in mitosis individual chromosomes align. (4) during anaphase I of meiosis, homologues separate and move to opposite poles; in mitosis, sister chromatids separate and move to opposite poles.

Excluding process, what are the overall fundamental differences between meiosis and mitosis?

(1)Meiosis requires two nuclear divisions; mitosis requires only one. (2) Meiosis produces four daughter nuclei, while mitosis produces two. (3)Meiosis daughter cells are haploid, while mitosis daughter cells are diploid like parent cells. (4)In meiosis, daughter cells are not genetically identical to each other or parent cells, while in mitosis, daughter cells are genetically identical to each other and the parent cell (5) Occurrence: meiosis only happens during certain times in life cycle of sexual organism; while mitosis happens often because it is how multicellular organism replaces damaged cells or evidence of growth in size.

How do you know if a trait(or) disorder is X-linked recessive

(1)displayed in males more than females. (2) skips a generation from grandfather to grandson (3)If a woman has it, all of the son's will have it

Independent assortment

(1)in genetics, the principle that genes are inherited independently of one another, although genes close together on the same chromosome have a higher likelihood of being inherited together (2) when homologues align at the metaphase plate, the maternal & paternal homologue orient toward either pole randomly; (3) homologous chromosome pairs separate independently or in a random manner. [caveat: do not confuse maternal & paternal chromosomes with the fertilized egg diploid. We are still talking about gametes, maternal and paternal refer to the organisms set of chromosomes he received from his/her parents. Not the chromosomes he will deliver to his/her offspring.]

trisomy

(2n+1) a type of aneuploidy in which an individual has three of a particular chromosome instead of the normal two; this conditions results from nondisjunction;

monosomy

(2n-1):a form of aneuploidy that occurs when an individual has only one chromosome(instead of the typical two) from a pair of homologues; this condition is the result of nondisjunction

Explain independent assortment with an example of a cell that has (a) 3 pairs of homologous chromosomes.(b) compare to humans who have 23 pairs...

(a) A cell with only three pairs of chromosomes(6 total) independently assort into 8(two cubed) combinations of maternal and paternal chromosomes. This variation was produced without even considering crossing over. If we consider an example where crossing over happens just once, the number of orientation jumps to 64(4 cubed). For humans who have 23 pairs, the possible orientations jumps to (2 raised to the 23rd) 8,338,608 arrangements.

(a) What is the start codon for translation? (b) what are the three stop codons?

(a) AUG (b) UGA, UAG, UAA

After transcription does the mRNA transcript (a) leave the nucleus? (b)What happens?

(a) No. (b)the mRNA transcript must be modified and processed before it can leave the nucleus.

What holds non-sister chromatids together (a) initially? (b)finally?

(a) Nucleoprotein lattice. (b) chiasmata

What is the (a) scientific name of the garden pea and (b) why was it a good choice for Mendel's experiments?

(a) Pisum sativum (b)This plant was easy to cultivate and had a short generation time. The peas could be cross pollinated by hand which allows for variable experimentation and the pea has many veritable traits to observe.

Name & classify the (a)5 mechanisms of eukaryotic gene regulation. (b) Which is most critical?

(a) [1] chromatin structure [2] transcriptional control [3] post-transcriptional control [4] translational control [5]post-translational control; first 3 control gene activity in the nucleus & the last two control mechanism occur in the cytoplasm; (b)The most critical control mechanism is transcriptional control.

What are (a)barr bodies? (b) How are they examples of heterochromatin & chromatin structure regulation?

(a) an extra X chromosome that becomes an inactive mass in males and females. (b)the genes contained within barr bodies do not get expressed because the chromatin is highly condensed.

What are the (a) 4 types of chromosomal structure mutation? (b) List some of the factors that may cause them

(a) deletion, translocation, duplication, & inversions (b) radiation, organic chemicals and viruses can cause chromosomes to mutate via breaking.

(a) The trp Operon is what kind of operon? (b)Explain how it works

(a) repressible operon; (b) If tryptophan is not present, structural genes are transcribed and the enzymes needed to synthesize tryptophan are produced. When tryptophan becomes present in abundance, these enzymes are no longer needed by the cell. This is the moment when the trp Operon is activated. tryptophan binds to an inactive repressor protein, thus activating it. The now active repressor bind to the operator and prevents transcription of structural genes. [Caveat...it should be noted that the regulator gene synthesizes inactive repressor protein whether tryptophan is absent or present. However when tryptophan[the corepressor] is present, it binds to the repressor, thus activating said repressor, and allowing it to perform its inhibitory function.]

How do things (a) leave the nucleus? (b) what leaves? (c) what doesn't leave?

(a) through nuclear pores(channel proteins). (b) mRNA leaves. (c) pre-mRNA/primary mRNA transcript can not.

(a) The lac Operon is what type of operon? (b)Explain how it works...

(a)inducible operon. (b) If lactose is not present in a bacterial cell, there is no need to express genes that code enzymes that catabolize it. But when glucose is not available and lactose is, structural genes are transcribed and the enzymes needed to catabolize lactose are produced. The regulator gene of the lac Operon codes for an active repressor. This repressor protein is ordinarily bound to the operator site and prevents transcription. [NOTE: you should note one difference between the lac & trp operons is that the trp Operon's regulator gene codes for an inactive repressor while the lac Operon's codes for an active repressor.] When lactose [or more specifically allolactose.] is present in the cell, it binds to the repressor thus deactivating it. The deactivation of the repressor now allows RNA polymerase to bind to the promoter,carry out transcription and, subsequently, synthesize the catabolic lactose enzymes. Lactose is called an inducer because it brings about the expression of the gene.

*Name a process and tell me where it happens in meiosis.

*Name a process and tell me where it happens in meiosis.

snRNPs

...

On the DNA template strand, what direction & location will transcription proceed

3'-to-5' direction...at the promoter sight

In what direction is the mRNA molecule built?

5'to 3'

true breeding

A genetically pure-breeding organism; an organism that when self-crossed produces offspring that have the same version of traits as it [the original parent]; Ex. If a plant is true breed for short leaves, all of its offspring will have short leaves.

operon model

A model used to explain gene regulation in prokaryotes;

Explain the difference between a promoter and a primer

A promoter is made of DNA and is the location where RNA polymerase attaches to transcribe a gene. Conversely, primer is made of RNA and is the initial segment needed to synthesize a complementary strand of DNA.

repressor

A protein that binds to an operator to prevent the transcription of DNA; also called repressor protein;

Transcription factors, activators and repressors are always present in the nucleus but they most likely have to be activated in some way before they bind to DNA. We don't know exactly how they are activated but what is the current prevailing thought?

A signaling/regulatory pathway that may use kinases[enzymes that phosphorylate] or phosphatases[enzymes that remove phosphate groups] to activate.

Briefly describe the structure of a ribosome?

A structure made of proteins and rRNA. rRNA is packaged with a variety of proteins into two ribosomal subunits(one subunit larger than the other). Ribosomes have a binding site for mRNA and three for tRNA.

Explain the connection between genetics and DNA.

An allele or gene is found on a strand of DNA. mRNA transcribes this gene & ribosomes synthesize that specific protein...The protein will display [or express] a specific phenotype. Overall, different alleles correspond to different version of a protein.

dominant allele

An allele that expresses its phenotypic effect even when heterozygous with a recessive allele; it is represented by an uppercase letter;

How does a cell ensure that the correct amino acid attaches to the correct tRNA molecule?

An enzyme, called aminoacyl-tRNA synthetases, contains a "lock-and-key like" recognition site for the correct amino acid.

inducible operon

An operon that initially is off [does not undergo transcription] but then gets turned on when the repressor protein is removed[deactivated] by the binding of an inducer. The lac Operon is an example of an inducible operon; inducible operons are usually involved in catabolic processes.

How do asexual organisms bring about genetic variation?

Asexual organisms rely on mutations. They do not possess the ability to create genetic variation through recombination.

Why are newborns with an abnormal sex chromosomes number more likely to survive than those with an abnormal autosome number?

Both males and females only have one function X chromosome. So extra copies don't really effect gene expression

How does binary fission in prokaryotes differ from mitosis and cytokinesis in eukaryotes?

Both processes are similar in that a parent cell forms genetically identical daughter cells. Said another way both processes produce copies of the original cell. Binary fission is asexual reproduction for prokaryotes which produces two new individuals, albeit identical ...Mitosis and cytokinesis is part of the growth process and is used for renewal and repair of damaged or old cells....binary fission does not involve the use of a mitotic spindle;

Explain CAP control of the lac operon....

CAP control involves the use of a molecule called cyclic AMP(cAMP). [1]When glucose is absent, cAMP accumulates in the cell. [2] A molecule of cAMP then binds to CAP, thus activating CAP to bind to DNA at the CAP binding site, adjacent to the lac promoter site. [3] When CAP binds to DNA, DNA bends exposing its promoter site to RNA polymerase. Only then does transcription occur. Now lets consider what happens when glucose is present. If present, only a small amount of cAMP is found in the cell. The CAP protein remains inactive and the lactose operon does not function maximally.

What's the difference between animal, plant and most fungi/ algae in terms of meiosis?

Cells produced via meiosis in animals are called gametes and will need to fuse with another cell to become living organisms. Cells produced via meiosis are called spores and develop into an organism without having to fuse with another spore. Fungi and algae do not ever have a diploid version and will always be haploid.

Chromosomes are the condensed version of chromatin existing whenever the cell divides. When the cell does not undergo division, chromosomes exists as chromatin. There are two version of chromatin. Name and briefly describe each.

Chromatin exists in one of two genetic states. It can occur as genetically active euchromatin or genetically inactive heterochromatin. Euchromatin appears as a loosely coiled, diffuse and lightly colored "string of beads." Because it is loosely coiled RNA polymerase and other factors needed for transcription can access the genes contained on DNA. Heterochromatin is a highly compacted, darkly stained "string of beads". It is considered genetically inactive because the DNA is so highly compacted that RNA polymerase cannot find or attach to DNA to transcribe genes. While one may infer that chromatin exist in one form or the other, the truth is that most cells exhibit both levels of compaction simultaneously. It just depends on which portion of the DNA strand is used more often.

How does chromatin structure affect gene expression?

Chromatin exists in one of two genetic states. It can occur as genetically active euchromatin or genetically inactive heterochromatin. Euchromatin appears as a loosely coiled, diffuse and lightly colored "string of beads." Because it is loosely coiled RNA polymerase and other factors needed for transcription can access the genes contained on DNA. Heterochromatin is a highly compacted, darkly stained "string of beads". It is considered genetically inactive because the DNA is so highly compacted that RNA polymerase cannot find or attach to DNA to transcribe genes. While one may infer that chromatin exist in one form or the other, the truth is that most cells exhibit both levels of compaction simultaneously. It just depends on which portion of the DNA strand is used more often.

Give examples of sex linked recessive genes?

Color blindness, hemophilia, muscular dystrophy.

What causes polyploidy?

Complete failure of meiotic spindle.

What has proven to be an essential process for the normal segregation of chromosomes during meiosis?

Crossing over

What accounts for the genetic dissimilarity between daughter cells and the parent cell following meiosis?

Crossing over.

transcription factors

DNA binding proteins that control transcription; groupings of transcription factors locate and bind to a single promoter [just adjacent to a gene]. They then attract and bind RNA polymerase. Transcription still may not occur until an activator or repressor binds initiating their own specific transcriptional effect.

transcription activators

DNA binding proteins the speed up transcription;

If DNA codes for proteins, where do carbohydrates, phospholipids & fats come from?

DNA codes for proteins and nucleic acid. Proteins(i.e. enzymes) make everything else.

What two "DNA-phrased" synonyms are used in place of chromatin & chromosomes?

DNA coil and DNA supercoil respectively.

Exhaustive explanation of DNA replication

DNA helicase unwinds the DNA helix by breaking H-bonds. On the leading strand (3' to 5') a molecule called DNA primase (RNA polymerase) adds a short segment of RNA (RNA primer) complementary to the initial 5' DNA nucleotide. This is due to the fact that DNA polymerase can only add nucleotides to the 3' carbon of a previous nucleotide. DNA polymerase adds DNA nucleotides (complementary to the leading strand) creating a contiguous new strand of DNA. DNA polymerase can only synthesize nucleotides in the 5' to 3' direction...Therefore the lagging (5' to 3') strand will be synthesized by DNA polymerase in short stretches of 5' to 3' resulting in Okazaki fragments. DNA primase puts a primer wherever it finds a 3' stretch of nucleotides and DNA polymerase adds the nucleotides. DNA ligase joins together Okazaki fragments of the lagging strand. After synthesizing is done DNA polymerase, proofreads strands, removes any primers, and replaces them with DNA nucleotides. Replication is not complete until RNA primers are removed

How does DNA replication in eukaryotes differ from prokaryotic DNA replication?

DNA in prokaryotes is circular and replication starts at the same point on the DNA molecule. This point is called the origin of replication. In eukaryotes DNA replication has many points of origin and the DNA is linear. It takes longer in eukaryotes. DNA bacterial cell replication can complete in 40 minutes while it takes hours in eukaryotes.

binary fission:

DNA is replicated and attaches to a special place on the plasma membrane indicating fission will happen. The cell elongates its plasma membrane and cell wall and the replicated DNA is pulled apart by the elongation. When the cell is approximately double its original length, the plasma membrane grows inward dividing the cell into two daughter cells.

The DNA in each eukaryotic chromosome is exactly 2 meters long. Describe the process that packages DNA to fit in the small spaces of a nuclear chromosome.

DNA is wound around 8 histones molecules giving it the appearance of a "string of beads." Each bead is called a nucleosome. Nucleosomes are joined by what is called "linker" DNA. This is the "string" component of the "string & beads." Linker DNA is folded into zig-zag patterns. It then loops back and forth into radial loops.

DNA primase

DNA primase is, in fact, a type of RNA polymerase which lays down a short segment of RNA needed to start DNA synthesis

transposons

DNA sequences that move between chromosomes & shut down genes;

In what arrangement do the chromosomes of (diploid) body cells occur?

Diploid body cells occur in pairs;

What causes down-syndrome?

Down syndrome is caused by an extra copy of chromosome 21. Reduced levels of crossing over have been linked to this issue.

Briefly describe why E. coli needs the trp operon...

E. Coli uses the trp operon to turn off the anabolic pathway that synthesizes tryptophan. If tryptophan is already present in E. coli, there is no reason to continue synthesizing more. E. coli uses trp operon to stop tryptophan production.

How is RNA different from DNA?

Each nucleotide monomer is made of a pentose sugar called ribose as opposed to deoxyribose, Adenine complementarily base pairs with uracil instead of thymine in DNA; RNA is single stranded as opposed to being double stranded.