Biology of Humans Exam 2!
Describe the appearance and location of the chromosomes during the stages of meiotic cell division, as pictured in 8.14.
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Mitosis is the division of the _______, while cytokinesis is the division of the ________.
Nucleus, Cytoplasm
In blood donations, blood type ____ is considered the universal donor, while type ____ is considered the universal recipient.
O, AB
Distinguish between the three general outcomes of natural selection: directional, disruptive, and stabilizing.
o Directional selection shifts the overall makeup of a population by selecting for one extreme phenotype. - Most common when local environment changes o Disruptive selection can lead to a balance between two or more contrasting phenotypes in a population. - Favored in patchy environments o Stabilizing selection favors intermediate phenotypes and selects against the extreme phenotypes - Typically occurs in relatively stable environments - Prevails most of the time
What is a reproductive barrier? What are the two main types?
• A reproductive barrier is anything that prevents individuals of closely-related species from interbreeding • Reproductive barriers can be classified as either prezygotic or postzygotic depending on whether they block interbreeding before or after the formation of zygotes (fertilized eggs)
What is a testcross? Refer to questions 16 & 17 in the Post Test of Chapter 9 on Canvas.
• A testcross is a mating between o an individual of dominant phenotype (but unknown genotype) and o a homozygous recessive individual
What is an exaptation? Give an example.
• An exaptation: - Is a structure that evolves in one context but becomes adapted for another function and - Is a type of evolutionary remodeling. • Exaptations can account for the evolution of novel structures. • Consider the evolution of birds from a dinosaur ancestor
What are sex-linked genes? Be able to work out problems like numbers 34-40 in the Activities Quiz of Chapter 9 on Canvas.
• Any gene located on a sex chromosome is called a sex-linked gene
What is biogeography? What is the difference between marsupial and placental mammals, and where are they found?
• Biogeography is the study of the geographic distribution of species • It is the first type of evidence that suggested to Darwin that today's organisms evolved from ancestral forms - Darwin noted that Galápagos animals resembled species of the South American mainland more than they resembled animals on similar but distant islands. • marsupials (mammals that complete embryonic development outside the uterus, typically in a mother's pouch) • placental mammals (mammals that complete embryonic development in the uterus) • Austrialia
What is cancer? Distinguish between the terms: tumor, malignancy and metastasis.
• Cancer is a disease of the cell cycle. • Cancer cells do not respond normally to the cell cycle control system. o They divide excessively and can invade other tissues of the body • Tumor: Cancer cells can form a tumor, an abnormally growing mass of body cells. • In benign tumors, the abnormal cells remain at their original site • Malignant tumors can spread to neighboring tissues and interrupt normal body functions • Malignancy: Malignant tumors can spread to neighboring tissues and interrupt normal body functions. A person with a malignant tumor is said to have cancer. • Metastasis: The spread of cancer cells beyond their original site of origin
What are the many ways in which gene expression can be regulated? Refer to Figure 11.3.
• Eukaryotic cells have more complex gene regulating mechanisms with many points where the process can be turned on or off. • The multiple mechanisms that control gene expression are like the many control valves along a water supply.
Define evo-devo. What is paedomorphosis?
• Evo-devo, or evolutionary developmental biology, is the study of the evolution of developmental processes in multicellular organisms. • Paedomorphosis: • Is the retention into adulthood of features that were solely juvenile in ancestral species • Has occurred in the evolution of • axolotl salamanders and • humans.
Define fossils. What is the fossil record?
• Fossils are imprints or remains of organisms that lived in the past - Often found in sedimentary rocks. • The fossil record is the ordered sequence of fossils as they appear in rock layers - It reveals the appearance of organisms in a historical sequence
Explain what homologous chromosomes are and how we inherit them. What are sex chromosomes? Which ones are found in males and females? What are autosomes?
• Homologous chromosomes are matching pairs of chromosomes that can possess different versions of the same genes. • Altogether, humans have 23 pairs of homologous chromosomes: o A pair of sex chromosomes: Females have two X chromosomes, while males have an X and a Y chromosome o Twenty-two pairs of matching chromosomes, called autosomes(any chromosome that is not a sex chromosome.)
What are homologous structures? What are vestigial structures?
• Homology is the similarity in structures due to common ancestry - It is illustrated by the remodeling of the pattern of bones forming the forelimbs of mammals for different functions. • Vestigial structures are remnants of features that served important functions in an organism's ancestors and - Now have only marginal, if any, importance - Examples include the rear leg bones evident in ancient whale fossils
How is cytokinesis different between animals and plants?
• In animal cells, cytokinesis is known as cleavage and o It begins with the appearance of a cleavage furrow, an indentation at the equator of the cell. • In plant cells, cytokinesis begins when vesicles containing cell wall material collect at the middle of the cell and then fuse o This leads to the formation of a membranous disk called the cell plate.
Describe the theory proposed by Lamarck to explain how species evolved.
• In the early 1800s, French naturalist Jean Baptiste Lamarck suggested that life evolves, and explained this evolution as the refinement of traits that equip organisms to perform successfully in their environment. • Lamarck proposed a mechanism called the inheritance of acquired traits • Basically, by using or not using its body parts, an individual may develop certain traits that it passes on to its offspring • This, of course, was an erroneous view of how species evolve • However, Lamarck helped set the stage for Darwin by proposing that species evolve as a result of interactions between organisms and their environment.
Which two scientists discovered that DNA was a double helix? They relied on X-ray crystallography data generated by which other scientist?
• James Watson and Francis Crick • Watson and Crick used X-ray crystallography data to reveal the basic shape of DNA • Rosalind Franklin produced the X-ray image of DNA
What role do homeotic genes play in multicellular organisms?
• Master control genes called homeotic genes regulate groups of other genes that determine what body parts will develop in which locations.
What is a mutagen? Give examples.
• Mutations may result from - errors in DNA replication or - physical or chemical agents called mutagens. • Many mutagens can act as carcinogens, agents that cause cancer • Although mutations are often harmful, they are the source of genetic diversity, which is necessary for evolution by natural selection.
Describe the technique of nuclear transplantation.
• Nuclear transplantation - Involves replacing the nucleus of an egg cell with the nucleus from a differentiated cell from an adult body cell - The recipient cell may then begin to divide to produce an early embryo, which ultimately develops into an adult.
What is meant by the term multiple alleles? What is the definition of codominance?
• The ABO blood groups in humans are an example of multiple alleles. • There are three common alleles: IA, IB and i - IA produces sugar A - IB produces sugar B - i produces neither A nor B • The three alleles in various combinations produce four phenotypes: A, B, AB, or O • IA and IB exhibit codominance: Both alleles are expressed in the phenotype. - So, an IAIB heterozygote will express both the A and B sugars, and will have phenotype AB • Both IA and IB are dominant over the i allele - So an IAi heterozygote will express sugar A, and an IBi heterozygote the B sugar - An ii homozygote cannot produce either the A or B sugar, and thus has phenotype O
According to the biological species concept a species is ...
• The biological species concept defines a species as: - "A group of populations whose members have the potential to interbreed with one another in nature to produce fertile offspring." - i.e: offspring that can reproduce
What is speciation?
• The diversity of life evolved through speciation, the process in which one species splits into two or more species. • Species can form by: • Allopatric speciation, due to geographic isolation • Sympatric speciation, without geographic isolation.
Gel electrophoresis is a method used to separate DNA fragments based on what two characteristics?
• The lengths of DNA fragments are compared using gel electrophoresis • It is a method for sorting macromolecules—usually proteins or nucleic acids—primarily by their: - Electrical charge - Size.
List in order (or better yet, draw out) the stages and events of the animal sexual life cycle. Include the role of meiosis and mitosis, and identify each stage as either haploid or diploid.
• The life cycle of a multicellular organism is the sequence of stages leading from the adults of one generation to the adults of the next. • Humans are diploid organisms in which: o Their somatic cells contain two sets of chromosomes o Their gametes are haploid, having only one set of chromosomes • In humans, a haploid sperm fuses with a haploid egg during fertilization to form a diploid zygote. • Sexual life cycles involve an alternation of diploid and haploid stages
Describe the structure of the DNA double helix, making use of the following terms or phrases: sugar-phosphate backbone, nitrogenous bases, helix, and complementary base-pairing. What type of chemical interaction holds the strands of a DNA molecule together?
• The model of DNA is like a rope ladder twisted into a spiral. - The ropes at the sides represent the sugar-phosphate backbones. - Each wooden rung represents a pair of bases connected by hydrogen bonds. • DNA bases pair in a complementary fashion - adenine (A) pairs with thymine (T) via two hydrogen bonds - cytosine (C) pairs with guanine (G) via three hydrogen bonds - Therefore, the more C & G a DNA double helix contains, the more stable it is
List the taxonomic hierarchy of classification, starting with genus and ending with domain.
• The taxonomic hierarchy extends to progressively broader categories of classification, from genus to: - Family - Order - Class - Phylum - Kingdom - Domain
Explain the basics of translation (shown in Figures 10.18 and 10.19); include in your answer the terms mRNA, ribosome, tRNA, complementary base pairing, start codon, stop codon, A site, P site, E site, amino acid, peptide bond, and translocation. 13. Explain the basics of translation (shown in Figures 10.18 and 10.19); include in your answer the terms mRNA, ribosome, tRNA, complementary base pairing, start codon, stop codon, A site, P site, E site, amino acid, peptide bond, and translocation.
• Translation is divided into three phases: 1. Initiation, 2. Elongation 3. Termination. • Initiation brings together 1. mRNA, 2. the initiator tRNA, with the first amino acid, Methionine (Met), attached, and 3. two subunits of the ribosome. • The mRNA molecule has a cap and tail that help the mRNA bind to the ribosome. • Initiation occurs in two steps. 1. An mRNA molecule binds to a small ribosomal subunit, then a special initiator tRNA binds to the start codon, where translation is to begin on the mRNA. 2. A large ribosomal subunit binds to the small one, creating a functional ribosome. • Elongation occurs in three steps. 1. Step 1: Codon recognition. • The anticodon of an incoming tRNA pairs with the mRNA codon at the A site of the ribosome. 2. Step 2: Peptide bond formation. • The polypeptide leaves the tRNA in the P site and attaches to the amino acid on the tRNA in the A site. • The ribosome catalyzes the bond formation between the two amino acids. 3. Step 3: Translocation. • The tRNA that was in the P site leaves the ribosome through the E site • The tRNA carrying the polypeptide moves from the A to the P site. • The mRNA and tRNA move as a unit • This movement brings into the A site the next mRNA codon to be translated, and the process can start again with step 1 • TERMINATION: • Elongation continues until a stop codon reaches the A site of the ribosome • Stop codons do not specify amino acids 1. Rather, they signify the end of translation • The completed polypeptide is freed, and the ribosome splits into its subunits
What are prions? List diseases they cause.
• Two classes of pathogens are smaller than viruses. 1. Viroids are small, circular RNA molecules that infect plants. 2. Prions are misfolded proteins that somehow convert normal proteins to the misfolded prion version, leading to disease. • Prions are responsible for neurodegenerative diseases including - mad cow disease, - scrapie in sheep and goats, - chronic wasting disease in deer and elk, and - Creutzfeldt-Jakob disease in humans.
What is X chromosome inactivation?
• X chromosome inactivation - Occurs in female mammals - Is when one of the two X chromosomes in each cell is inactivated at random • All of the descendants will have the same X chromosome turned off.
Define macroevolution. What does it include?
• macroevolution, evolutionary change above the species level - Including the origin of evolutionary novelty and new groups of species
Using molecular biology techniques, the evolutionary relationships among species can be determined by comparing _____ and ______ of different organisms.
Genes, Proteins
What two main points did Darwin propose in his Origin of Species? 3. What two main points did Darwin propose in his Origin of Species?
• Darwin made two main points in The Origin of Species. 1. Organisms inhabiting Earth today descended from ancestral species. 2. Natural selection is the mechanism for descent with modification.
Describe evolutionary trees.
• Darwin saw the history of life as analogous to a tree: - The first forms of life on Earth form the common trunk - At each fork is the last common ancestor to all the branches extending from that fork. - The tips of millions of twigs represent the species living today. • Biologists represent these patterns of descent with an evolutionary tree
What is non-disjunction?
• In nondisjunction, − the members of a chromosome pair fail to separate during anaphase, − thus producing gametes with an incorrect number of chromosomes. • Nondisjunction can occur during meiosis I or II. • If nondisjunction occurs, and a normal sperm fertilizes an egg with an extra chromosome, the result is a zygote with a total of 2n + 1 chromosomes. • If the organism survives, it will have an − an abnormal karyotype and − probably a syndrome of disorders caused by the abnormal number of genes.
Distinguish between pleiotropy and polygenic inheritance. (Just know the definition. You will not be required to solve problems in this case.)
• Pleiotropy is when a single gene influences several characters. • Polygenic inheritance is the additive effects of two or more genes on a single phenotype
Define prezygotic barriers. List the five main examples.
• Prezygotic barriers prevent mating or fertilization between species. • These include: - Temporal isolation - Habitat isolation - Behavioral isolation - Mechanical isolation - Gametic isolation
Explain the normal function of proto-oncogenes and tumor suppressor genes in cells. How does this function change when cancer-causing mutations occur in each type of gene?
• Proto-oncogenes are normal genes with the potential to become oncogenes - They are found in many animals - They often are genes that code for growth factors, proteins that stimulate cell division. • A cell can acquire an oncogene - from a virus or - from the mutation of one of its own proto-oncogenes. • Changes in genes whose products inhibit cell division are also involved in cancer • Tumor-suppressor genes encode proteins that normally help to inhibit cell division - Prevent uncontrolled cell growth • A mutation in these genes that prevent their normal function would contribute to cancer
What is a restriction enzyme? Does it cut DNA at random or only at specific sites?
• The production of recombinant DNA actually requires two enzymes: - the restriction enzyme, which produces pieces of DNA called restriction fragments with "sticky ends" important for joining DNA from different sources • After a restriction enzyme binds to its recognition sequence, it cuts the two strands of DNA at specific points within the sequence
Two patterns have been proposed to describe the pace of evolution: the gradual pattern and the punctuated equilibria pattern. Distinguish between these two.
• There are two contrasting patterns for the pace of evolution: 1. The gradual pattern, in which big changes (speciations) occur by the steady accumulation of many small changes, and 2. The punctuated equilibria pattern, in which there are long periods of little apparent change (equilibria) interrupted (punctuated) by relatively brief periods of rapid change.
Explain the basics of transcription (shown in Figures 10.13 and 10.14); include in your answer the terms promoter, RNA polymerase, terminator, template strand, and complementary base pairing.
• Transcription - makes RNA from a DNA template, - uses a process that resembles the synthesis of a DNA strand during DNA replication, and - substitutes uracil (U) for thymine (T). • RNA nucleotides are linked by the transcription enzyme RNA polymerase. • The "start transcribing" signal is a nucleotide sequence called a promoter, which is located in the DNA at the beginning of the gene. a. The first phase of transcription is initiation, in which: i. RNA polymerase attaches to the promoter and ii. RNA synthesis begins. b. During the second phase of transcription, called elongation, i. the RNA grows longer and ii. the RNA strand peels away from its DNA template. c. During the third phase of transcription, called termination, i. RNA polymerase reaches a special sequence of bases in the DNA template called a terminator, signaling the end of the gene, ii. polymerase detaches from the RNA and the gene, and iii. the DNA strands rejoin.
Define the following terms transcription factors, enhancers, activators, silencers.
• Transcription in eukaryotes, unlike in prokaryotes, is complex - It involves many proteins, called transcription factors, that bind to DNA sequences called enhancers. • Repressor proteins called silencers - Bind to DNA and - Inhibit the start of transcription. • Activators are - More typically used by eukaryotes than silencers and - Turn genes on by binding to DNA.
What is the function of tRNA? What are the two business ends?
• Transfer RNA (tRNA) acts as a molecular interpreter • Must carry out two distinct functions - 1) Pick up the appropriate amino acid - 2) Recognize the appropriate codon in mRNA • It has two business ends: - At one end, the amino acid attaches - At the other, there is a special triplet of bases called the anticodon • It is complementary to the codon in mRNA
What is a virus? What is a bacteriophage? Compare and contrast the lytic and lysogenic cycles.
• Viruses share some, but not all, characteristics of living organisms. Viruses - possess genetic material in the form of nucleic acids wrapped in a protein coat, - are not cellular, and - cannot reproduce on their own. • In a sense, a virus is nothing more than "genes in a box." • Bacteriophages, or phages, are viruses that attack bacteria. • They typically consist of an elaborate protein-based structure consisting of: - Head, which encloses a molecule of DNA - Tail, which is used to inject the DNA into the host bacterial cell - Tail fibers, which are used for attachment • Phages have two reproductive cycles. - In the lytic cycle, • many copies of the phage are produced within the bacterial cell, and • then the bacterium lyses (breaks open). - In the lysogenic cycle, • the phage DNA inserts into the bacterial chromosome and • the bacterium reproduces normally, copying the phage at each cell division.
A population is ....
• population, a group of individuals of the same species living in the same place at the same time, changes over generations.
Define the following terms: heredity, trait and character.
− Heredity is the transmission of traits from one generation to the next. − A character is a heritable feature that varies among individuals. − A trait is a variant of a character.
What are the three domains of life? Which type of organisms or kingdoms do they contain? In other words, know Figure 14.25 well.
* Earliest organisms • Domain Bacteria • Domain Archaea • Domain Eukarya > The protists (Multiple Kingdoms) > Kingdom Plantae > Kingdom Fungi > Kingdom Animalia
What is meant by a true-breeding variety of an organism?
*Referring to organisms for which sexual reproduction produces offspring with inherited traits identical to those of the parents. The organisms are homozygous for the characteristics under consideration. • Mendel o Created true-breeding varieties of plants o Crossed two different true-breeding varieties • Hybrids are the offspring of two different true-breeding varieties. o The parental plants are the P generation. o Their hybrid offspring are the F1 generation. o A cross of the F1 plants forms the F2 generation.
What is the role of DNA ligase in the creation of recombinant DNA molecules?
- DNA ligase, which connects the DNA pieces into continuous strands by forming bonds between adjacent nucleotides.
Be able to use a Punnett Square to determine the genotypic and phenotypic ratios of the offspring of a genetic cross. For examples: Refer to Figure 9.6, and questions 5-7 in the Post Test of Chapter 9 on Canvas.
...
Describe the appearance and the location of the chromosomes during the four stages of mitotic cell division, as pictured in Figure 8.7.
1. (A) Prophase: 2. (B) Metaphase: 3. (C) Anaphase: 4. (D) Telophase:
What are the two phases of the cell cycle? What are the three stages of interphase?
1. Interphase 1. G1 (Gap 1): Cell is growing and preparing for DNA synthesis 2. S (Synthesis): Chromosomes are duplicated 3. G2 (Gap 2): Cell is growing and preparing for cell division 2. The mitotic phase
What are the three important roles of cell division?
1. Replaces damaged or lost cells 2. Permits growth 3. Allows for reproduction
What are the three main types of cancer treatment?
1. Surgery, which removes the tumor 2. Radiation therapy, which damages DNA and disrupts cell division 3. Chemotherapy, which uses drugs that disrupt cell division
The textbook presents five lines of evidence in support of evolution. List them.
1. The fossil record 2. Biogeography 3. Comparative anatomy 4. Comparative embryology 5. Molecular biology
Compare and contrast mitosis and meiosis with regard to: 1) the number of cell divisions, 2) the number of daughter cells produced, 3) the number of chromosomes in each cell before and after each process, and 4) their function(s) in animals. In other words, make sure you know Figure 8.15 well.
1. The number of cell divisions varies: - Mitosis uses one division and produces two diploid cells - Meiosis uses two divisions and produces four haploid cells • All the events unique to meiosis occur during meiosis I. − Pairing of homologous chromosomes − Crossing-over • Meiosis II is virtually identical to mitosis in that it separates sister chromatids − But unlike mitosis, meiosis II yields daughter cells with a haploid set of chromosomes
. Individuals with Down syndrome have an extra chromosome _____, which gives them a total of ____ chromosomes in each cell. The incidence of this disease increases with the age of the _____.
21, 47, mom
When do independent assortment of chromosomes, crossing over between homologous chromosomes, and random fertilization occur during sexual reproduction? Explain how each increases genetic variation.
Independent Assortment of Chromosomes • When aligned during metaphase I of meiosis, the side-by-side orientation of each homologous pair of chromosomes is a matter of chance. • Every chromosome pair orients independently of the others during meiosis. • For any species the total number of chromosome combinations that can appear in the gametes due to independent assortment is: • 2n where n is the haploid number. • For a human, n = 23 • 223 = 8,388,608 different chromosome combinations possible in a gamete Random Fertilization • A human egg cell is fertilized randomly by one sperm, leading to genetic variety in the zygote. • If each gamete represents one of 8,388,608 different chromosome combinations, at fertilization, humans would have 8,388,608 × 8,388,608, or more than 70 trillion, different possible chromosome combinations! • Note: If crossing-over is considered, the number is even much higher than that Crossing Over • In crossing over, nonsister chromatids of homologous chromosomes exchange corresponding segments − This leads to genetic recombination, or the production of gene combinations different from those carried by parental chromosomes
According to the multiplication rule, the probability of a compound event is the _______ of the separate probabilities of the independent events.
Product
Assume tall (T) is dominant to dwarf (t). If a homozygous dominant individual is crossed with a homozygous dwarf, the offspring will __________.
all be tall
If a homozygous dominant is crossed with a homozygous recessive for a given trait, the offspring will be __________.
all of the dominant phenotype
RNA processing includes the addition of a _____ and a ____ to protect the RNA and enhance its translation by _________. It also involves RNA splicing, which involves the removal of _______ (regions that do not code for proteins) and the joining of _______ (protein-coding regions). The end result is a mature _________ RNA
cap, tail, ribosomes, introns, exons, messenger
Mendel demonstrated two basic laws of heredity by following the inheritance of a single trait over three generations (a monohybrid cross, as in Figure 9.5) and by following two traits (a dihybrid cross as in Figure 9.8). List these two laws, explain their meanings, and state which type of cross (mono- or di-) demonstrated each.
o A monohybrid cross is a cross between two true-breeding parent plants that differ in only one character. o A dihybrid cross is the crossing of parental varieties differing in two characters. o What would result from a dihybrid cross? Two hypotheses are possible: 1. Dependent assortment 2. Independent assortment o Mendel's dihybrid cross-supported the hypothesis that each pair of alleles segregates independently of the other pairs during gamete formation. Thus, the inheritance of one character has no effect on the inheritance of another. This is the law of independent assortment.
How are the ABO blood groups determined? What are the various genotypes and phenotypes? Be able to work out inheritance problems involving these various groups. For example, questions 36-39 in the Post Test of Chapter 9 on Canvas.
o ABO blood group system, the classification of human blood based on the inherited properties of red blood cells (erythrocytes) as determined by the presence or absence of the antigens A and B, which are carried on the surface of the red cells. Persons may thus have type A, type B, type O, or type AB blood. o Thus, blood type O is considered the universal donor, because the red blood cells of these people have NO antigens o Blood type AB, on the other hand, is the universal recipient, because the red blood cells of these people have NO antibodies
Define the following terms: allele, homozygous, heterozygous, dominant, recessive, phenotype, genotype.
o There are alternative versions of genes, called alleles. o . For each character, an organism inherits two alleles, one from each parent. o An organism is homozygous for that gene if both alleles are identical. o An organism is heterozygous for that gene if the alleles are different. o . If two alleles of an inherited pair differ o The allele that determines the organism's appearance is the dominant allele o The other allele, which has no noticeable effect on the appearance, is the recessive allele o Geneticists distinguish between an organism's physical traits and its genetic makeup. o An organism's physical traits are its phenotype. o An organism's genetic makeup is its genotype.
The textbook emphasizes three key but subtle points about evolution by natural selection: 1) It is ________, and not individuals, that evolve 2) Natural selection can amplify or diminish only _______ traits 3) Evolution is not _______: it does not lead to perfectly adapted organisms This is because _________ factors vary from time to time and place to place
population, heritable, goal-directed, enviromental
What is Darwinian fitness?
• "Survival of the fittest" is misleading if we take it to mean direct competitive contests between individuals • Fitness is the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals. • Thus, the fittest individuals in the context of evolution are those that produce the largest numbers of viable, fertile offspring, and thus pass on most genes to the next generatio
Define clade.
• A clade: - Consists of an ancestral species and all its evolutionary descendants - Forms a distinct branch in the tree of life. • Cladistics is based on the Darwinian concept of "descent with modification from a common ancestor."
What are codons? How many are there? How many specify or code for amino acids? How many stop codons are there? What is special about the AUG codon?
• A codon is a triplet of bases, which codes for one amino acid. • There are 64 codons (base triplets) - 61 code for amino acids - 3 are stop codons, instructing the ribosomes to end the polypeptide. • AUG has a dual function: i) Codes for methionine, and ii) Acts as start codo
What is a family pedigree?
• A family pedigree o Shows the history of a trait in a family o Allows geneticists to analyze human traits
What is a mutation? What is the difference between base substitution, insertion and deletion?
• A mutation is any change in the nucleotide sequence of DNA. • Mutations can change the amino acids in a protein. • Mutations within a gene can occur as a result of base substitutions, deletions, or insertions • Base substitution is the replacement of one base by another • Because of redundancy of the genetic code, some substitution mutations have no effect • Nucleotide deletion is the loss of a nucleotide • Nucleotide insertion is the addition of a nucleotide • Insertions and deletions can • change the reading frame of the genetic message, and so • lead to disastrous effects
How many subunits does a ribosome contain? List the type of RNA they contain, as well as the three tRNA binding sites.
• A ribosome is made up of two subunits - Each subunit is made up of proteins and a considerable amount of another kind of RNA, ribosomal RNA (rRNA). • A fully assembled ribosome holds tRNA and mRNA for use in translation • The ribosome consists of three tRNA binding sites: - P site= Holds the tRNA carrying the growing poplypeptide chain - A site = Holds a tRNA carrying the next amino acid to be added to the peptide chain - E (Exit) site = Provides the exit site for tRNAs that have unloaded their amino acids
What are carcinogens? Give examples.
• Cancers can be caused by carcinogens, cancer-causing agents, found in the environment, including: - Tobacco products - Alcohol - Exposure to ultraviolet light from the sun.
What is convergent evolution? Distinguish between analogous structures and homologous structures. Give an example of analogous structures.
• Convergent evolution involves superficially similar structures from different evolutionary branches that result from natural selection shaping analogous adaptations. • Similarity due to convergence is called analogy, not homology. - E.g.: The wings of birds and insects are analogous flight equipment: - They evolved independently and are built from entirely different structures • To develop phylogenetic trees and classify organisms according to their evolutionary history, we use only homologous similarities • A major clue to distinguishing homology from analogy; - The more complex two similar structures are, the less likely it is they evolved independently - E.g. Skulls of a human and a chimpanzee
Explain the basics of DNA replication (shown in Figures 10.6 and 10.7); include in your answer the terms DNA polymerase, template strand, and complementary base pairing. If the sequence of a parental (or template strand) is AAGCTCG, then the sequence of the new daughter strand would be ....
• DNA replication ensures that all the body cells in multicellular organisms carry the same genetic information. • It is also the means by which genetic information is passed along to offspring • The logic is simple: If you know the sequence of bases in one strand, you can determine the sequence of the other strand by base-pairing rules • Example: If sequence 1 is AGTC, then sequence 2 must be TCAG • DNA polymerases: − Are enzymes − Make the covalent bonds between the nucleotides of a new DNA strand − Are involved in repairing damaged DNA.
Define the terms transcription and translation.
• DNA specifies the synthesis of proteins in two stages: 1. Transcription, the transfer of genetic information from DNA into an RNA molecule 2. Translation, the transfer of information from RNA into a protein. • "Genetic information in DNA is • transcribed into RNA, then • translated into polypeptides, • which then fold into proteins."
Distinguish between the terms: DNA, gene, chromosome, replicated chromosome, sister chromatid and centromere.
• DNA: The DNA in a cell is packed into an elaborate, multilevel system of coiling and folding. • Gene: a molecular unit of heredity of a living organism. • Chromosome: the structures that contain most of the organism's DNA. • Replicated Chromosome: a chromosome that has made a copy of itself • Sister Chromatid: Before a cell divides, it duplicates all of its chromosomes, resulting in two copies called sister chromatids. • Centromere: Sister chromatids are joined together at a narrow "waist" called the centromere.
What three parts does every nucleotide have? What are the four bases in DNA?
• Each nucleotide is composed of three components: • Nitrogenous base • Phosphate group • Deoxyribose (SUGAR) • The four nucleotides found in DNA differ in their nitrogenous bases. These bases are: • thymine (T), cytosine (C), adenine (A), and guanine (G).
Distinguish between embryonic and adult stem cells.
• Embryonic stem cells (ES cells) - are derived from blastocysts and - can give rise to all the specialized cells in the body. • Adult stem cells are cells in adult tissues - Generate replacements for some of the body's cells (the non-dividing differentiated cells) • Unlike embryonic ES cells, adult stem cells - Are partway along the road to differentiation - Usually give rise to only a few related types of specialized cells.
Distinguish between silent, missense and nonsense mutations.
• Example: A mutation that changes a GAA codon to GAG. Since both code for the same amino acid (Glu - Gutamic acid), the change is called a silent mutation • missense mutation: it changes the encoded amino acid • Some base substitutions are called nonsense mutations, because they change an amino acid codon into a stop codon • Example: A mutation that changes an AGA (Arginine) codon to UGA (stop) codon • The result will be a prematurely terminated protein, which likely will not function properly
What is gene flow?
• Gene flow is a source of evolutionary change where a population may gain or lose alleles when fertile individuals move into or out of the population • Tends to reduce genetic differences between populations
The chromosome theory of inheritance states that ....
• Genes are located at specific positions on chromosomes and the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns
Define genetic drift. Compare and contrast the founder effect and the bottleneck effect.
• Genetic drift is a change in the gene pool (genetic composition) of a small population due to chance. • Occurs via two main ways • Bottleneck effect • Founder effect • This genetic drift due to a drastic reduction in population size is termed the bottleneck effect • Disasters such as earthquake, floods, fires, epidemics, may kill large numbers of individuals, producing a small surviving population that is unlikely to have the same genetic makeup as the original population • The genetic drift due to the establishment of a small, new population whose gene pool differs from that of the parent population is called the founder effect • Genetic drift is also likely when a few individuals colonize an isolated island, lake, or other new habitat • The smaller the colony, the less its genetic makeup will match the gene pool of the large population from which the colonist emigrated
HIV is a retrovirus. What does that mean? What is the role of reverse transcriptase?
• HIV is a retrovirus, an RNA virus that reproduces by means of a DNA molecule. • Retroviruses use the enzyme reverse transcriptase to synthesize DNA on an RNA template
Compare and contrast reproductive cloning and therapeutic cloning.
• In 1997, Scottish researchers produced Dolly, a sheep, by a procedure called reproductive cloning, because it results in the birth of a new animal. • They used an electric shock to fuse adult somatic cells with eggs from which the nuclei had been removed • After several days of growth, some resulting embryos were implanted in the uteruses of surrogate mothers • As expected, Dolly resembled her genetic parent, the nucleus donor, not the egg donor or surrogate mom • The purpose of therapeutic cloning is not to produce a viable organism but to produce embryonic stem cells REPRODUCITVE CLONING: Implant embryo in surrogate mother>>> Clone of donor is born THERAPEUTIC CLONING: Remove embryonic stem cells from embryo and grow in culture>> >Induce stem cells to form specialized cells for therapeutic use
Compare and contrast sexual and asexual reproduction.
• In asexual reproduction: Single-celled organisms reproduce by simple cell division • Sexual reproduction: requires fertilization of an egg by a sperm using a special type of cell division called meiosis. o Thus: • Meiosis for reproduction • Mitosis for growth and maintenance
What is cellular differentiation? What is gene expression?
• In cellular differentiation, cells become specialized in structure and function • In gene expression • A gene is turned on and transcribed into RNA • Information flows from • Genes to proteins • Genotype to phenotype. • Information flows from DNA to RNA to proteins
What is incomplete dominance? Be able to work out problems such as the cross shown in Figure 9.18. In other words, anticipate the phenotypic and genotypic ratios of crosses involving white/red/pink snapdragons. An example is question 35 in the Post Test of Chapter 9.
• In incomplete dominance, F1 hybrids have an appearance in between the phenotypes of the two parents. • For example, when red snapdragons are crossed with white snapdragons, all the F1 hybrids have pink flowers
Darwin based his theory of natural selection on which two key observations? What was his inescapable conclusion regarding these observations?
• Observation 1: Overproduction and competition - All species have the potential to produce many more offspring than the environment can support. - This leads to competition among individuals ("struggle for existence") • Observation 2: Individual variation • Variation exists among individuals in a population. • Much of this variation is heritable. • Conclusion: Unequal reproductive success (natural selection) - Those individuals with traits best suited to the local environment generally leave a larger share of surviving, fertile offspring.
Define postzygotic barriers. List the three main examples
• Postzygotic barriers operate if interspecies mating occurs and hybrid zygotes form • These include: - Reduced hybrid viability - Reduced hybrid fertility - Hybrid breakdown
List the three main differences between DNA and RNA.
• RNA differs from DNA in three main ways: o It has uracil (U) in place of thymine o It has ribose instead of deoxyribose o It is typically single-stranded
Recall how to name species scientifically. Organisms are given a two part name, italicized and latinized, and with the first letter of the genus capitalized. The names can also be underlined instead of italicized. Examples: Homo sapiens or Homo sapiens
• Scientific names ease communication by: - Unambiguously identifying organisms - Making it easier to recognize the discovery of a new species. • Carolus Linnaeus (1707-1778) proposed the current taxonomic system based upon: - A two-part name for each species - A hierarchical classification of species into broader groups of organisms.
What is sexual dimorphism?
• Sexual dimorphism is a distinction in appearance between males and females - Due largely to secondary sexual traits that are not directly associated with reproduction or survival - Examples: Manes on lions, antlers on deer, and colorful plumage on peacocks and other birds
What is sexual selection?
• Sexual selection is a form of natural selection in which inherited characteristics determine mating preferences - In some species, secondary sex structures may be used to compete with members of the same sex for mates - In a more common type of sexual selection, individuals of one sex (usually females) are choosy in selecting their mates
What are microRNAs?
• Small single-stranded RNA molecules, called microRNAs (miRNAs), bind to complementary sequences on mRNA molecules in the cytoplasm. • After binding, some miRNAs trigger the breakdown of their target mRNA, whereas others block translation.
Compare and contrast allopatric speciation and sympatric speciation.
• Species can form by: - Allopatric speciation, due to geographic isolation - Sympatric speciation, without geographic isolation.
Distinguish between systematics and taxonomy.
• Systematics focuses on: - Classifying organisms - Determining their evolutionary relationships. • Taxonomy is the: - Identification of species - Naming of species - Classification of species • Systematics includes taxonomy.
The machinery used to translate mRNA requires four ingredients. List them.
• The machinery used to translate mRNA requires - ATP, - enzymes, - ribosomes, and - transfer RNA (tRNA).
What are the three main causes of evolutionary change?
• The main causes of evolutionary change are - Genetic drift - Gene flow - Natural selection • Natural selection is the most important, because it is the only process that promotes adaptation.
