BIOB51 University Of Toronto MIDTERM REVIEW AND PRACTICE QUESTIONS

BIOB51 Midterm 2 Review

End of Chapter Textbook Questions (Assigned in Lecture)

Chapter 1

5.         The idea behind multidrug therapy for HIV is to increase the number of mutations required for resistance and thus reduce genetic variation in the viral population for survival in the presence of drugs. Could we achieve the same effect by using antiretroviral drugs in sequence instead of simultaneously? Why or why not?

No, we could not achieve the same result if we administer the drugs in a sequence. The unfortunate result would likely be development of resistance to all the drugs. This is because the HIV population would only have to develop resistance for one drug at a time, which is quite easy for it to do. The key to multiple drug therapy is that the drugs are given simultaneously, so that HIV virions must have four or five simultaneous mutations (one for each drug) to survive. Even with HIV's high mutation rate and large population size, the simultaneous occurrence of multiple resistance mutations in one virion is unlikely.

17.       Question 5 concerned treating HIV by using multiple drugs sequentially instead of simultaneously. For a clinical trial comparing these strategies, see: Gulick, R. M., J. W. Mellors, et al. 1998. Simultaneous vs sequential initiation of therapy with Indinavir, Zidovudine, and Lamivudine for HIV-1 infection: 100-week follow-up. JAMA 280: 35.

Chapter 2

2. Consider the experiment described in Section 2.1 in which Ted Garland and colleagues bred mice to run long distances on exercise wheels. We presented the results as evidence that two dozen generations of selective breeding had altered the experimental population. How does the control strain support this interpretation? If Garland had simply compared the behavior of the 24th experimental generation to the behavior of the first experimental generation, would the evidence for evolution be as strong? Explain.

Strong evidence of evolution is seen in the results that come from selective breeding. In the Garland et al. experiment on mice, microevolution could be observed after only 24 generations of selection. The experimental design and procedure was designed to measure the effect of selection and the change of the population. From a large population of mice, the researchers chose high-runner lines and control lines, each with 10 mated pairs. They needed to keep track of each generation in the experiment, because they selected a male and female which run the greatest distance, to produce the next generation. On the contrary, the control strains had male and female pairs chosen at random in each generation. Female mice from the selected lineages ran almost three times faster than the control mice. This is direct evidence that population and species change over time.

Chapter 3

8(Part 1). Describe three major objections to Darwin’s theory in the 19th century that were eventually resolved by discoveries by other scientists in the 20th century.

Three major objections to Darwin's theory in the 19th century were: there is not enough variability for evolution to continue for very long; new traits would disappear by "blending" with other traits; and, the earth's temperature implies that the earth is too young for evolution to have occurred. These were resolved by the discoveries, respectively, of mutation, genes, and radioactivity.

Chapter 4

9. What is homoplasy? Why does homoplasy make it more challenging to estimate evolutionary history?

Homoplasy is defined as a similarity in traits that is not due to inheritance (not derived) from a common ancestor. Homoplasy is misleading because it makes species that are not closely related appear as if they are closely related. If the genetic and developmental basis of a morphological trait is known, then researchers can distinguish homology from homoplasy. Morphological traits can also be measured in fossil species. Compared to morphological traits, DNA sequence data are relatively easy to acquire in large amounts, but can be subject to extensive homoplasy.

Chapter 5

17. Chromosome number can evolve by smaller-scale changes than duplication of entire chromosome sets. For example, domestic horses have 64 chromosomes per diploid set while Przewalski’s horse, an Asian subspecies, has 66. Przewalski’s horse is thought to have evolved from an ancestor with 2n = 64 chromosomes. The question is: Where did its extra chromosome pair originate? It seems unlikely that an entirely new chromosome pair was created from scratch in Przewalski’s horse. To generate a hypothesis explaining the origin of the new chromosome in Przewalski’s horse, examine the adjacent figure. The drawing at right shows how certain chromosomes synapse in the hybrid offspring of a domestic horse–Przewalski’s horse mating (Short et al. 1974). The remaining chromosomes show a normal 1:1 pairing. Do you think this sort of gradual change in chromosome number involves a change in the actual number of genes present?

The most likely explanation is that the long chromosome found in domestic horses split into two pieces in the ancestor of Przewalski's horse. If the two smaller segments still synapse with the long chromosome during matings between hybrids, then it is likely that gene number and order is unchanged.

20. Figure 5.12 presented evidence that people with certain genotypes for the serotonin transporter gene are more sensitive to maltreatment during childhood. For an exploration of possible benefits associated with the sensitive genotype, see: Homberg, J. R., and K. P. Lesch. 2011. Looking on the bright side of serotonin transporter gene variation. Biological Psychiatry 69: 513–519.

Chapter 6

1. List the five conditions that must be true for a population to be in Hardy–Weinberg equilibrium. Why is it useful to know the conditions that prevent evolution? For each condition, specify whether violation of that assumption results in changes in genotype frequencies, allele frequencies, or both.

The five conditions are: no selection, no mutation, no migration, no chance events (also can be stated as infinite population size, or no genetic drift), and random mating. Violation of selection, mutation, migration, and/or chance events will result in changes in allele frequencies and genotype frequencies in the population. Violation of random mating—but not the others—will result in changes in genotype frequencies but not in allele frequencies.

Textbook Questions (Assigned in Tutorial)

Chapter 3

1.      In everyday English, the word adaptation means an adjustment to environmental conditions. How is the evolutionary definition of adaptation different from the everyday English sense?

The everyday meaning of "adaptation" refers to a change that occurs in a single individual's lifetime, while the evolutionary meaning refers to a trait that has developed via natural selection over many generations. An evolutionary adaptation is also defined strictly in terms of relative reproductive fitness, while the everyday meaning can refer to changes that do not necessarily affect reproduction

2.      a. Describe Darwin’s four postulates in your own words. What would have happened in the snapdragon experiment if any of the four had not been true? b. If Darwin’s four postulates are true for a given population, is there any way that evolution cannot happen? What does this imply about whether evolution is or is not occurring in most populations today?

a.       The four postulates are, briefly: variation exists, the variation is heritable, survival and reproduction are not equal, and survival and reproduction are not random. In the snapdragon experiment, if there had been no variation, all flowers would have been the same color. If variation had not been heritable, the colors of the best-reproducing plants would not have been passed to their offspring. If there had not been unequal survival and reproduction, all plants would have attracted equal numbers of bees and produced equal numbers of seeds. If survival and reproduction had been random, some plants would have had more bee visits and produced more seeds than other plants, but the difference would not be related to plant color. In any of these four cases, the snapdragon population would not have evolved. 

b.      If the four postulates are true, a population is virtually certain to evolve unless selection is extremely weak and genetic drift is very strong. Since the four postulates are almost always true, virtually all populations of organisms are evolving today, at least with regard to some genetic loci.

4.      According to the text, it is correct to claim that most finches died from starvation during the 1977 drought because “there was a strong correspondence between population size and seed availability.” Do you accept this hypothesis? If so, why don’t the data in Figure 3.13 show a perfect correspondence between when seed supply started falling and when population size started to drop?

The claim that the vanished finches probably died of starvation is certainly reasonable given the data in Figure 3.13 and the absence of obvious other causes such as increased predation or disease. The graphs in Figure 3.13 show that most small, soft seeds disappeared between about July and October of 1976, the same time that the bird population began to decline. Seeds were still abundant at first, but they were predominantly large seeds. Then, even the large seeds began disappearing, and the bird population continued to decline sharply. The birds did not all die instantaneously because it takes time for an animal to starve to death, and some individuals were likely able to scratch for the few remaining small seeds for several months before succumbing to starvation.

5.      A common creationist criticism of the finch study is, “But it’s just a little change in beak shape. Nothing really new has evolved.” Or put a different way, “It’s just microevolution and not macroevolution.” The finch team continues to spend a great deal of effort on their project— traveling thousands of miles to the remote Galápagos every year, just to try to band an entire population of birds and all their nestlings and measure their bills. How would you respond to the creationists’ criticisms? Do you think the ongoing 30-year-effort of the finch bill project has been worthwhile? Is it useful to try to document microevolution, and does it tell us anything about how macroevolution might work?

Many answers are possible. Though it may be "just" microevolution, the shape of a bird's bill is not a minor feature for the bird—it is the bird's one and only food-handling tool. Furthermore, microevolution and macroevolution are not a dichotomy, macroevolution is simply microevolution carried out for a long time. The changes that most laypeople would consider "macroevolution" typically require hundreds of thousands of years to evolve, so it is not logical to expect to observe them in a single field study. Evolutionary biologists generally regard long-term studies of microevolution as highly informative for learning how natural selection happens in a natural environment, and for a close-up look at the causes of small changes that, eventually, can add up to macroevolution.

Chapter 4

5.      What is a synapomorphy?

Synapomorphy is a characteristic that is shared by two or more species and also derived. This means that it was modified in a common ancestor and then inherited by the descendant species.

9.   What is homoplasy? Why does homoplasy make it more challenging to estimate evolutionary history?

Homoplasy is defined as a similarity in traits that is not due to inheritance (not derived) from a common ancestor. Homoplasy is misleading because it makes species that are not closely related appear as if they are closely related. If the genetic and developmental basis of a morphological trait is known, then researchers can distinguish homology from homoplasy. Morphological traits can also be measured in fossil species. Compared to morphological traits, DNA sequence data are relatively easy to acquire in large amounts, but can be subject to extensive homoplasy.

Chapter 5

1.    What is the difference between genetic variation, environmental variation, and genotype-by-environment interaction? Give examples of each. Try to think of potential examples not covered in this chapter.

Genetic variation is based on differences in alleles (versions of a gene) and ultimately the entire genomes, among the individuals. Genetic variation is necessary for evolution, since these differences are encoded and transmitted from one generation to the next. For example, genetic variation in a blood type gene in humans, results in four different phenotypes. In this case, three different alleles of one gene are: I A, I B, i (where I A and IB are codominant, while allele i is recessive to either one). Different combinations of these alleles produce four possible phenotypes: A, B, AB and O blood types, with different frequencies in different parts of the world. 

Environmental variation is based on the differences produced when same genotypes are exposed to different environments. This usually happens because certain environments might alter gene expression. For example one genotype in a species of plants, often produces different sizes of mature plants, when grown in the different altitudes or with different soil nutrients. Similarly, dark pigmentation on the tips of ears and paws of Siamese cats develops in certain latitudes with colder temperatures. Many additional examples of traits that could vary a great deal under environmental changes are found in quantitative traits. 

Genotype by environment variation is based on both differences in the genomes and ways that environment affects the phenotypes. When one genotype develops different phenotypes in different environments, we could say that this genotype exhibits phenotypic plasticity. For example, a change from asexual to sexual reproduction, based on the amount of nutrients, predation or parasitism. Phenotypic plasticity can also evolve.

5.      Consider the nucleotide sequence TGACTAACGGCT. Transcribe this sequence into mRNA. Use the genetic code to translate it into a string of amino acids. Give an example of a point mutation, an insertion, a deletion, a frameshift mutation, a synonymous substitution, a nonsynonymous substitution, and a nonsense mutation. Which of your examples seem likely to dramatically influence protein.

Example answer: 
DNA: TGACTAACGGCT 
RNA: ACUGAUUGCCGA 

Polypeptide: Threonine-Aspartic Acid-Cysteine-Arginine 

A point mutation, such as T to G in the DNA strand, gives CCU for the first codon and that would replace amino acid threonine with proline. 

An insertion or a deletion would cause a frame-shift. For example, a deletion in DNA: TGACTAACGGCT, leaves mRNA sequence as: ACGAUUGCCGA and the polypeptide would be: 
Threonine-Isoleucine-Cysteine. Duplication/insertion of a single base also causes a frameshift, since each codon has three bases. This also affects the rest of the sequence. 

If the polypeptide change remains the same due to a change where DNA has one base-pair change, yet same amino acid remains in its place, we use the term synonymous substitution. For example ACU codes for Threonine, but if there is a silent substitution of ACU to ACC, ACG or ACA, the amino acid will remain in its place. The protein will function the same, with such mutation. A silent site mutation does not change the amino acid specified by a codon; a replacement mutation does. 

If there is a substitution of one amino acid to another, due to the base-pair change in DNA and RNA, we use the term non-synonymous substitution. 

A nonsense mutation will bring a stop codon, instead of an amino acid. Example is UUA for Leucine, might become a stop codon with one base change (UGA). Nonsense mutations probably affect the carrier most dramatically, because they do not allow polypeptide chain to grow.

7.      How many redheads live in a village of 250 people, where the frequency of red hair is 0.18?

If there are 250 people in the village and 18% of them have red hair, there are 45 red heads in the village.

15. Suppose a silent mutation occurs in an exon that is part of the gene for TAS2R38 in a human. Has a new allele been created? Defend your answer.

A silent mutation in the gene for TAS2R38 in human would create a new allele, because the DNA sequence will be different, yet it might not have any phenotypic effects, if the amino acids that are responsible for tasting PTC remain the same.

Chapter 6

1.      List the five conditions that must be true for a population to be in Hardy–Weinberg equilibrium. Why is it useful to know the conditions that prevent evolution? For each condition, specify whether violation of that assumption results in changes in genotype frequencies, allele frequencies, or both.

The five conditions are: no selection, no mutation, no migration, no chance events (also can be stated as infinite population size, or no genetic drift), and random mating. Violation of selection, mutation, migration, and/or chance events will result in changes in allele frequencies and genotype frequencies in the population. Violation of random mating—but not the others—will result in changes in genotype frequencies but not in allele frequencies.

2.     Why was it important that G. H. Hardy used variables in his mathematical treatment of changes in population allele frequencies across generations? Would it have been equally useful to simply work several more examples with different specific allele frequencies?

The use of variables allowed Hardy to prove the general case: that—given the five assumptions—any allele frequencies will stay in equilibrium. Before this proof, it was not intuitively clear to most people that the specific allele frequencies did not matter. As is often the case, general proofs expressed mathematically can reveal important patterns that were not always intuitively obvious beforehand.

3.    Name the phenomenon being described in each of these (hypothetical) examples, and describe how it is likely to affect allele frequencies in succeeding generations.

A) Migration followed by natural selection. The frequency of the T allele is likely to increase rapidly. 

B) Migration followed by natural selection. The frequency of the T allele may increase, but only slowly, and perhaps not at all, due to the rarity of the T allele and the weakness of selection. 

C) Frequency-dependent selection. The frequency of small males is likely to gravitate toward a stable equilibrium frequency, at which small and large males have identical fitness. 

D) Under dominance. One allele will very likely go to fixation, and the other allele will be lost. Which allele is lost is likely to depend on where the initial allele frequencies are, relative to the unstable equilibrium point. 

E) Heterozygote superiority, or over dominance. The frequency of the m allele is likely to gravitate toward a stable equilibrium frequency.

OA

1.      An entire village of 500 people were tested for sensitivity for bitter-tasting foods. How many people are non-tasters where frequency of non-tasters in this population is 0.29?

500 x 0.29 = 145

2.      If a mutational change occurs in the normal sequence 5' - ATTATACACAGAGAGTTT -3' to change it to  5'- ATTATACACAGAGTTT -3' which term best describes the mutation or possible cause?

Deletion of AG

3.      Use the table to answer the question. Which of the following is the outgroup?

Presence (1) or Absence (0) of Hox Genes

	Hox1	Hox2	Hox3	Hox4	Hox12
Mouse	1	1	1	1	1
Snail	1	1	1	1	0
Flatworm	1	1	1	1	0
Sea anemone	1	1	0	0	0
Sponge	0	0	0	0	0

Sponge

4.      The Hardy-Weinberg term p gives:

Allele frequency

5.      Black colour in horses is governed by homozygosity of the recessive allele at the A locus: black coloured horses have aa while horses with other nonblack colours may be AA or Aa at the same locus. Assuming the alleles are at Hardy-Weinberg equilibrium, what best describes the genotype frequency of black horses in a population of Arabian horses? 2pq?

6.       Which of the following phrases best fits the term SNP?

Two different nucleotides appear at the same position in genomic DNA from different individuals

7.      Socially parasitic ants form a group that includes S. daguerrei, the ancestor of socially parasitic species and all its descendents: ____ .

Clade

8.      The S . saevissima species group contains socially polymorphic species which form a ____ group.

Monophyletic

9.      At the level of the species, the mtDNA phylogeny excludes some of the ancestors of this group: it is a _______ group.

Polyphyletic

10.  A _______ based on morphological characters, is an evolutionary hypothesis for the relationships between the S. saevissima species.

Phylogeny

11.  This study confirmed that ___ originated once among these ants.

Polygyny (multiple queens)

12.  Among ______ S. invicta ants there are some colonies that accept only one queen and other colonies that accept multiple queens

Socially polymorphic

13.  Choose all that apply to complete the sentence. Examples of homoplasy include _____ .

	A.	Spots on leopard geckos and leopards
	B.	Streamlined bodies in dolphins and ichthyosaurs
	D.	Bobbed tails in bobcats and lynx
	F.	Eyes on the top of the head in caiman and hippos

14.  Researchers studied snapdragon plants and their bumblebee pollinators. The researchers found that after two generations white-flowered snapdragon plants had higher reproductive success than did yellow-flowered snapdragon plants. Which of the following statements about the role of bumblebees should form part of their conclusion?

Bumblebees are the agents of selection: they chose to pollinate the white-flowered plants and this resulted in higher reproductive success for the white flowered snapdragons.

15.  Choose the best option to complete the sentence. If an adaptation is a product of natural selection the trait will __________.

be a heritable trait that raises the fitness of individuals more than any other trait that has appeared in the species over evolutionary time.

16.  Homozygosity at the recessive a locus gives albinism in whales. Researchers counted the number of albino and the number of normally pigmented whales in a population. The number of normally pigmented whales divided by the total population gives:

Phenotype frequency

1/15 ;2pq

17.  Go to OMIM (see link in OA1 folder) type in 602421 to go to Cystic Fibrosis. Scroll down on the 602421 cystic fibrosis page to find "Allelic Variants" .0001 and find the information needed to identify which of the options below would best complete the following sentence. In the Saguenay-Lac-Saint-Jean region of Quebec De Braekeleer estimates that the carrier rate is  ____ which would correspond to ____ if the population is at Hardy-Weinberg equilibrium.

18.  On an island there are many cats with short tails. The alleles for tailless are tightly linked to a short tandem repeat DNA marker. Researchers sampled 150 cats identifying 60 homozygous for the wildtype 6-repeat STR; 90 short-tailed cats that were heterozygous for the wildtype 6-repeat STR allele but they did not find any cats homozygous for the 10- repeat STR allele associated with tailless. What are the genotype frequencies in this population? HINT: write out the genotypes. Chose all the answers that apply.

	a.	0.4 (6,6)
	b.	0.6 (6,6)
	c.	0.16 (10,10)
	d.	0.4 (10,6)
	e.	0.4 (10,10)
	f.	0.6 (10,6)

Chapter 8

7. How can you identify an allele that has experienced recent strong positive selection?    

Ans)  Loci that have been under recent positive selection will usually be in linkage disequilibrium with nearby neutral markers (indicate an allele of young age), and will be at relatively high frequency for the allele's age.  

8.  Populations of rats exposed to the poison warfarin rapidly evolve resistance. The gene for warfarin resistance is located on rat chromosome 1. Michael Kohn and colleagues (2000) surveyed rats in five German rat populations known to vary in their recent exposure to warfarin and in their resistance. The researchers determined the genotype of each rat at a number of marker loci near the warfarin resistance gene. For each population, the researchers calculated the average heterozygosity (H) among the marker loci, the fraction of loci that were out of Hardy–Weinberg equilibrium (HWE), and the fraction of marker–locus pairs that were in linkage disequilibrium (LD). Their results appear in Figure 8.32. Based on these graphs, rank the five populations in order, from lowest to highest, for exposure to warfarin and resistance. Explain your reasoning.    

Ans) Strong positive selection tends to cause high linkage disequilibrium and tends to lower heterozygosity. Therefore we can deduce that the x-axis must start with low resistance on the left, and go to high resistance on the right. The most resistant population should be WU, and the least resistant should be LH

This deduction is correct: the most resistant rat population is WU, followed by BK, PS, HT, and LH. In the original graphs, the x-axis goes from 0% resistance on the left to 100% resistance on the right.

Chapter 9

1. Degree of antisocial behavior is a quantitative trait in human males. Avshalon Caspi and colleagues (2002) used data on several hundred men to investigate the relationship between antisocial behavior and two factors. The first factor was genotype at the locus that encodes the enzyme monoamine oxidase A (MAOA). MAOA acts in the brain, where it breaks down a variety of the neurotransmitters nerve cells use to communicate with each other. The gene for MAOA is located on the X chromosome. Due to genetic differences in the gene’s promoter, some men have low MAOA activity and others have high MAOA activity. The second factor was the experience of maltreatment during childhood. Based on a variety of evidence, the researchers determined whether each man had experienced no maltreatment, probable maltreatment, or severe maltreatment. The data are summarized in Figure 9.34.

a. Is the variation among men in antisocial behavior at least partly due to differences in genotype? Explain.

b. Is the variation among men in antisocial behavior at least partly due to differences in environment? Explain.

c. Do men with different genotypes respond the same way to changes in the environment? Explain.

d. Is antisocial behavior heritable? Explain.

e. Do these data influence your opinion about how men who exhibit antisocial behavior should be treated

and/or punished?                               

Ans) A) The figure shows that variation in antisocial behavior is correlated with differences in genotype. It is possible that the correlation is due to some other factor (for example, certain genotypes may be more common in certain ethnic groups, which may be exposed to certain environments). However, if we leave that possibility aside, we can tentatively conclude that MAOA genotype is associated with antisocial behavior.

B) Yes, because different levels of childhood maltreatment (an environmental condition) are associated with different levels of antisocial behavior. If there were no effect of environment, both lines would have a slope of 0 (parallel to the x-axis).

C) Men with different genotypes respond in the same direction: for men in both MAOA categories, increased maltreatment is associated with heightened antisocial behavior. However, the strength of this effect is different in the two groups. Men with the low MAOA activity genotype appear more strongly influenced by environment than are men with the high MAOA activity genotype. The line for men with low MAOA activity has a greater (steeper) slope than the line for men with high MAOA activity, indicating a stronger effect of the environment factor on the x-axis.

D) Yes. This means simply that some of the variation in antisocial behavior is attributable to genotype.

E) The answer to this question is left to the reader.

4. Suppose you are telling your roommate that you learned in biology class that within any given human population, height is highly heritable. Your roommate, who is studying nutrition, says, “That doesn’t make sense, because just a few centuries ago most people were shorter than they are now, clearly because of diet. If most variation in human height is due to genes, how could diet make such a big difference?” Your roommate is obviously correct that poor diet can dramatically affect height. How do you explain this apparent paradox to your roommate?      

Ans) High heritability within a population does not mean that variation between populations is due to genetic differences. If the populations differ in an environmental factor, the variation between populations can be due entirely to environment. In this case, your roommate is comparing height between two populations (a medieval population versus a modern population) that differ in dietary environment.

5. Now consider heritability in more general terms. Suppose heritability is extremely high for a certain trait in a certain population.

a. First, can the trait be strongly affected by the environment despite the high heritability value? To answer this question, suppose that all the individuals within a certain population have been exposed all their lives to the same level of a critical environmental factor. Will the heritability value reflect the fact that the environment is very important?

b. Second, can the heritability value change if the environment changes? To answer this question, imagine that the critical environmental factor changes such that different individuals are now exposed to different levels of this environmental factor. What happens to variation in the trait in the whole population? What happens to the heritability value?       

Ans)   A) Yes, the trait may be strongly affected by environment. But no matter how important the environment could potentially be, if there is little variation in environment, the heritability value will typically be very high.

B) Heritability values will often change if the environment changes. Typically, if a formerly invariant environment begins to change, heritability values will decrease.

 Chapter 10 questions

4. What is an evolutionary trade-off? Why do they occur? Give two examples. How does the occurrence of tradeoffs illuminate the general question of whether all traits are adaptive?      

Ans) A trade-off is a situation in which an increase the fitness of one trait will inevitably lead to a decrease in fitness of another trait. This can occur due to developmental constraints, or simply because organisms have a limited pool of energy and cannot develop all traits to a maximum degree simultaneously. Examples include testis size versus brain size in bats, and flower size versus number of flowers in begonias. The occurrence of trade-offs demonstrates that a particular trait can be adaptive in one context, yet the same trait can be non-adaptive in a different context.

11. Suppose that fish were introduced into Lake Citadelpark, one of the lakes De Meester studied. What do you predict will happen to phenotypic plasticity in the Daphnia of Lake Citadelpark? Outline the observations you would need to make to test your prediction.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 

Ans) A logical prediction is that Daphnia in Lake Citadelpark would evolve greater phenotypic plasticity in phototactic behavior if fish were introduced into the lake. To test this prediction, we could allow a number of generations to pass, then repeat De Meester's experiment. We could then isolate many individual genotypes and allow them to reproduce asexually in the laboratory, producing many replicates of each genotype. Each genotype could then be tested for phototactic behavior, both in water that had never had fish in it, and also in water that came from the lake. If the prediction is correct, then members of each genotype will show strong negative phototaxis in normal (fish-inhabitated) lake water and much weaker negative phototaxis in water that had never had fish in it.

OA 2 (ans still not 100%)

The neutral theory predicts that as a result of genetic drift the rate of accumulation of nonsynonymous substitutions will be slower because __________

ANS:

An article about lizards in the Dominican Republic notes that lizards in the Greater Antilles are an example of "replicated adaptive radiation". What is adaptive radiation?

ANS: Splitting of group of lizards into populations that became adapted to many different ecological niches

 The Q and D genes are 20 map units apart: the recombination rate r= 0.2. In the cross Qd/ qD x qd/ qd what fraction of the progeny will be QD/ qd?

ANS:

A mating between two related individuals is Consanguineous

The article titled "Population genetics of the white phased spirit black bear of British Columbia " written by Hedrick and Ritland was published in the journal Evolution in the year 2012 ,volume 66 pages 305 – 313

The neutral theory predicts that as a result of genetic drift the rate of accumulation of nonsynonymous substitutions will be slower because __________.

ANS: They are often deleterious mutations and are removed by natural selection

Fruit flies have gene timeless with two allals: Is-tim and s-tim. How could researchers identify whether the Is-tim allele has experienced recent strong positive selection at a site in Italy called Novoli? Among the fruit flies from the Novoli population…

ANS:  The Is-tim allele would be at high frequency and high linkage disequilibrium with nearby marker loci

A gene D is linked to its marker G. Linkage means … The genotype for the tightly linked loci on the chromosome

Marker “G” is characterized by three single nucleotide polymorphisms, the haplotype would be … tendency for alleles at different loci on a chromosome to be inherited together

Researchers tested whether gene and marker locus were in linkage equilibrium within a population. Linkage equilibrium is… tendency for genotypes at one locus to be randomly distributed with respect to genotypes at another locus

Inbreeding is mating among kin

The Q and D genes are 20 map units apart: recombination rate r = 0.2. In cross Qd/qD x qd/qd. What fraction of progeny will be QD/qd?

10%

In a population of mice at an interesting genetic locus for which the recessive m alleles do not make a functional protein. If researchers estimate mutation rate to be 0.9x10^-4 and they know that the selection coefficient is 0.9, what is the equilibrium frequency for the maintenance of alleles at this locus?

ANS:

Q = sqrt(u/s) u = 0.9x10^-4, s = 0.9

0.01

If the bear cub in the article is not albino, but a white-phase bear because it has the same genotype as a Kermode bear in Ritland and Marshall (2001), then the bear cub will be heterozygous at Cys at codon 298 that codes for MC1R from its mother and father.

ANS:

*In a plant population linkage disequilibrium is complete between branch length locus (B) and presence of a marker “e”. If the marker absence is “E” then what must be true of this plant population?

ANS:

Branch length locus and marker e are on different chromosomes?

*If a student was working on an experimental population of pea plants. The student crossed plants that were reddish-purple and gave long pollen to other plants that were pink and gave round pollen and he wrote the genotypes of the plants in cross: R L / r l x r l / r l. (Flower colour = R=reddish-purple, r = pink) and pollen shape (L = long, r = round). Choose best option for completing sentence in his notebook. If the two loci, flower colour and pollen shape, are not linked, l would expect ____ of progeny of this cross to be R L / r l.

ANS:

75%

Among a population of 220 bears on a small island the frequency of the MC1R298Cys was 0.1 and the population was at Hardy Weinberg equilibrium. Then 30 black bears migrated to the small island from the mainland where the MC1R298Tyr was fixed. What are the new allele frequencies of the admixed population? Choose all the frequencies needed to complete the sentence. Among the admixed island population the f(MC1R298Tyr )= p= ______ and  f(MC1R298Cys) = q= ________  , the new allele frequencies indicate that the island population has evolved as a consequence of the migration.

ANS: 0.01, 2, 0.81, 0.18, 0.088, 0, 1, 0.912

Researchers analyzed genotypes of all 30 bunnies from a small island population and found 5 of them were genotype AG: they were heterozygous at a SNP in the ASIP gene. If frequency of A allele of SNP is 0.33 what is fixation index of population?

ANS: 0.11, 1, 0.44, 0.63, 0.18