Genetic Analysis: An Integrated Approach (3rd Edition)
3rd Edition
ISBN: 9780134605173
Author: Mark F. Sanders, John L. Bowman
Publisher: PEARSON
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Chapter 20, Problem 14P
Directional selection presents an apparent paradox. By favoring one allele and disfavoring others, directional selection can lead to fixation (a frequency of
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Suppose that a population is at equilibrium between mutation and selection for a deleterious recessive allele, where s = 0.5 and μ = 10−5. What is the equilibrium frequency of the allele? What is the selection cost?
In mice, black fur (W) is dominant over white fur (w). In an ideal mouse population exhibiting Hardy–Weinberg equilibrium, 177 mice out of 236 have white fur.
Calculate the number of mice that are heterozygous dominant for the fur colour gene in the population.
Selection confers a reproductive advantage to individuals based on their adaptations, and therefore causes the alleles carried by those individuals to increase in the population. Selection can be simulated by having your partner remove any three individuals of a particular suit as you deal the cards into a pile. The fitness of that variant is therefore 0.77 (10/13 survive), while the fitness of the other three variants remains at 1.0 (13/13 survive). Recalculate allelic (suit) frequencies after selection.
1. What is the effect of selection on reproduction, allelic diversity, and frequency?
2. What would happen if similar selection continued over several generations?
Cite references.
Chapter 20 Solutions
Genetic Analysis: An Integrated Approach (3rd Edition)
Ch. 20 - 20.1 Compare and contrast the terms in each of the...Ch. 20 - In a population, what is the consequence of...Ch. 20 - 20.3 Identify and describe the evolutionary forces...Ch. 20 - Describe how natural selection can produce...Ch. 20 - Thinking creatively about evolutionary mechanisms,...Ch. 20 - 20.6 Genetic drift, an evolutionary process...Ch. 20 - Over the course of many generations in a small...Ch. 20 - Catastrophic events such as loss of habitat,...Ch. 20 - 20.9 George Udny Yule was wrong in suggesting that...Ch. 20 - 20.10 The ability to taste the bitter compound...
Ch. 20 - Figure 20.6 illustrates the effect of an ethanol ...Ch. 20 - 20.12 Biologists have proposed that the use of...Ch. 20 - 20.13 Two populations of deer, one of them large...Ch. 20 - 20.14 Directional selection presents an apparent...Ch. 20 - 20.15 What is inbreeding depression? Why is...Ch. 20 - 20.16 Certain animal species, such as the...Ch. 20 - Genetic Analysis 20.1 predicts the number of...Ch. 20 - 20.18 In a population of rabbits, and . The...Ch. 20 - Sickle cell disease (SCD) is found in numerous...Ch. 20 - 20.20 Epidemiologic data on the population in the...Ch. 20 - The frequency of tasters and nontasters of PTC...Ch. 20 - Tay-Sachs disease is an autosomal recessive...Ch. 20 - 20.23 Cystic fibrosis (CF) is the most common...Ch. 20 - 20.24 In the mouse, Mus musculus, survival in...Ch. 20 - 20.25 In a population of flowers growing in a...Ch. 20 - Assume that the flower population described in the...Ch. 20 - 20.27 ABO blood type is examined in a Taiwanese...Ch. 20 - 20.28 A total ofmembers of a Central American...Ch. 20 - 20.29 A sample offield mice contains individuals...Ch. 20 - Prob. 30PCh. 20 - Albinism, an autosomal recessive trait...Ch. 20 - 20.32 The frequency of an autosomal recessive...Ch. 20 - 20.33 Evaluate the following pedigree, and answer...Ch. 20 - Evaluate the following pedigree, and answer the...Ch. 20 - The following is a partial pedigree of the British...Ch. 20 - Draw a separate hypothetical pedigree identifying...Ch. 20 - Prob. 37PCh. 20 - 20.38 Achromatopsia is a rare autosomal recessive...Ch. 20 - 20.39 New allopolyploid plant species can arise by...
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- Recall that the Hardy-Weinberg model makes the following assumptions: No mutations Extremely large population No gene flow No selection You score flower colour in a very large natural population where flower colour is a co-dominant trait where white and red are homozygotes (CWCW and CRCR) and pink are heterozygotes (CWCR). Taking your observed phenotypes and genotypes, you apply the Hardy-Weinberg principle and find an excess of homozygous individuals (that is, individuals with either white or red flowers). Give two plausible explanations for this excess of homozygotes in the natural population.arrow_forwardIs it likely that the selection coefficient (s) is similar in value for the three populations shown? Is it important to know if the amount of genetic variation for the trait under selection is approximately equal in all three populations in the graph? Why or why not?arrow_forwardWhich of the following is the LEAST CONVINCING argument against micromutationism? Advantageous mutations of large effect are more resistant to loss by drift than advantageous mutations of small effect. Mutations of small effect are more likely to be advantageous than mutations of large effect. Empirical studies suggest that some adaptive traits are governed at least in part by loci of large phenotypic effect.arrow_forward
- Eugene Eisen selected for increased 12-day litter weight (total weight of a litter of offspring 12 days after birth) in a population of mice (E. J. Eisen. 1972. Genetics 72:129–142). The 12-day litter weight of the population steadily increased, but then leveled off after about 17 generations. At generation 17, Eisen took one family of mice from the selected population and reversed the selection procedure: in this group, he selected for decreased 12-day litter weight. This group immediately responded to the reversed selection: the 12-day litter weight dropped 4.8 g within 1 generation and dropped 7.3 g after 5 generations. On the basis of the results of the reverse selection, what is the most likely explanation for the leveling off of 12-day litter weight in the original population?arrow_forwardThere are two existing hypotheses for an unusually high frequency of a deleterious recessive allele in a certain population other than it is hidden in the heterozygous genotype and not exposed to selection. Explain what these two likely hypotheses are and how you could distinguish between them based on your understanding of the applicable assumptions that are part of the Hardy-Weinberg Equilibrium Modelarrow_forwardEvolution is driven by both nonrandom and random mechanisms. Identify the mechanisms of evolution that are random and comment on how they affect allele frequencies across generations.arrow_forward
- Assume that the frequency of gene B in a hypothetical population Is 0.63, that there are only two alleles (B and b) of the gee in the population, that allele B is dominant over allele b, that neither allele has a selective advantage over the other, and that the population is at equilibrium with regard to this particular gene. What proportion of the population is expected to have the phenotype specified by the B allele according to the Hardy-Weinberg formula? 0.47 0.87 0.67 0.40 0.37arrow_forwardA population of mealworm beetles (Tenebrio molitor) called the founder generation-consisting of 150 Black (MM) individuals, 100 Brown (Mm) individuals and 250 Orange (mm) individuals-is established on a remote region of Puerto Rico. Mating within this population occurs at random, the three genotypes are selectively neutral and mutations occur at a negligible rate. (a) What are the frequencies of alleles M and m in the founder generation? Frequency of allele M= Frequency of allele m= (b) Calculate p2, 2pq, q2 and the expected number of MM individuals, Mm individuals, and mm individuals in the population, assuming that the population is in Hardy-Weinberg equilibriumarrow_forwardArtificial selection is when people selectively choose individuals with a certain desired trait to use as parents of the next generation. It is done to domesticated (or semi-domesticated) organisms. It has produced such monstrosities as bubble-eyed goldfish, revealing the potential for selection acting on heritable variation to produce varieties appearing very different than their ancestors. How is that different from natural selection? (Select all that apply) A- In artificial selection, humans directly cause new mutations to occur, whereas natural selection relies on mutations that occur randomly over time. B- Artificial selection can lead to organisms that would be unfit to survive in the wild, whereas natural selection usually makes the population better adapted. C- Artificial selection is directed ahead of time towards an intentional goal; not so with natural selection. D- Really, they are exactly the same process. Both cause what seems to be design without a designer. E-…arrow_forward
- You are a scientist studying a population of beetles. Beetle color is controlled by two alleles at a single genetic locus. AA beetles are blue, Aa purple, and aa pink. You count 30 blue beetles, 10 purple beetles, and 40 pink beetles. a) What is the frequency of the A allele? [ Select ] b) What is the observed frequency of the Aa genotype? 1 Select ] c) Under Hardy-Weinberg equilibrium, what is the expected frequency of the aa gentoype? [ Select ] d) Is this beetle population evolving? I Select ]arrow_forwardIn Manx cats, the recessive allele for tail length can be lethal. A heterozygous dominant genotype results in a shortened tail, while a homozygous dominant genotype results in a normal tail. A homozygous recessive genotype is lethal. In an ideal Manx cat population exhibiting Hardy-Weinberg equilibrium, if the lethal allele has a frequency of 0.22, what percentage of the Manx cat population retains a shortened or normal tail length? Express your answer using three significant digits.arrow_forwardIf gene A/a is not in Hardy-Weinberg equilibrium due to natural selection such that individuals with the genotype AA have a fitness value of 1.0, heterozygotes have only slightly reduced fitness at 0.9, and individuals with the genotype aa have a fitness value of 0.6, what kind of change in allele frequency would you expect to see over time assuming you start with equal frequencies of the 2 alleles?arrow_forward
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