EBK CAMPBELL BIOLOGY IN FOCUS
2nd Edition
ISBN: 8220101459299
Author: Reece
Publisher: PEARSON
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Textbook Question
Chapter 21.3, Problem 2CC
Distinguish genetic drift from gene flow in terms of (a) how they occur and (b) their implications for future
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Three basic predictions underlie genetic drift in populations: (1) As long as the population size is finite,some level of genetic drift will occur; thus, withoutnew mutations, all variation will drift either to fixationor to loss. (2) Drift happens faster in small populationsthan in large populations. (3) The probability that anallele is fixed (goes to a frequency of 1.0) is equal toits initial frequency (p) in the population, while itsprobability of loss from the population due to drift isequal to 1 − p. Given these three predictions:a. What is the allele frequency of a new autosomalmutation immediately after it occurs in a diploidpopulation of size N = 100,000?b. What is the allele frequency of a new autosomalmutation immediately after it occurs in a diploidpopulation of size N = 10?c. In which population does the new mutation have ahigher probability of going to fixation by chancewith genetic drift?
The evolution of a qualitative trait in reponse to natural selection is described by the following equation,
R=h2 S
a) What is S and what does it measure?
b) Describe a study that woukd allow you to estimate S in a real population.
Genetic equilibrium means that ...
O the distribution of alleles is not changing from
generation to generation
The distribution of alleles is changing from
generation to generation
O the gene pool is not affected by a catastrophic
event
O the gene pools is not affected by selective agents
Chapter 21 Solutions
EBK CAMPBELL BIOLOGY IN FOCUS
Ch. 21.1 - Explain why genetic variation within a population...Ch. 21.1 - Of all the mutations that occur in a population,...Ch. 21.1 - Prob. 3CCCh. 21.2 - A population has 700 individuals, 85 of genotype...Ch. 21.2 - The frequency of allele a is 0.45 for a population...Ch. 21.2 - WHAT IF? A locus that affects susceptibility to a...Ch. 21.3 - In what sense is natural selection more...Ch. 21.3 - Distinguish genetic drift from gene flow in terms...Ch. 21.3 - WHAT IF? Suppose two plant populations exchange...Ch. 21.4 - What is the relative fitness of a sterile mule?...
Ch. 21.4 - Explain why natural selection is the only...Ch. 21.4 - Prob. 3CCCh. 21 - Natural selection changes allele frequencies...Ch. 21 - No two people are genetically identical, except...Ch. 21 - Sparrows With average-sized w1ngs survive severe...Ch. 21 - If the nucleotide variability of a locus equals...Ch. 21 - There are 25 individuals in population 1, all with...Ch. 21 - A fruit fly population has a gene with two...Ch. 21 - FOCUS ON EVOLUTION Using at least TWO examples,...Ch. 21 - Prob. 9TYUCh. 21 - SYNTHESIZE YOUR KNOWLEDGE This kettle lake formed...
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- Discuss the significance of the HardyWeinberg principle as it relates to evolution and list the five conditions required for genetic equilibrium.arrow_forward1. What is the expected time to fixation in generations for a new mutation in a diploid population (like humans) with an effective population size of 50? This new mutation is neutral and has no impact on fitness (e.g. synonymous polymorphism). Assuming the mutation isn’t lost immediately, will it reach fixation faster in a population of Ne=500 or Ne=5,000 and why?arrow_forwardWhat is meant by the term genetic variation? Give two examplesof genetic variation . What causesgenetic variation at the molecular level?arrow_forward
- Scientific studies have shown that the majority of human genetic differences worldwide exist within groups (or races) rather than between groups. True or false?arrow_forward. In a population of 50,000 diploid individuals, what isthe probability that a new neutral mutation will ultimately reach fixation? What is the probability that itwill ultimately be lost from the population?arrow_forwardWhat historical, social, religious, cultural, and economic factors promote genetic drift in humans? Can you think of some specific human groups in which genetic drift is likely to have occurred?arrow_forward
- O Mutation-selection balance Suppose that one allele A₁ mutates to another allele A2 at some rate, μ. Suppose as well that A₁ is dominant over A2 such that A₁A1 and A₁A2 both have the same fitness, but that individuals that are homozygous recessive (A2A2) for the mutant allele A2 are less fit than the dominant genotype by some amount s, the selection coefficient. In this case, A2 mutant alleles come into the population at rate µ, and are removed from the population only when the show up in homozygous genotypes. The gory mathematical proof can be found in Box 7.8, which tells us that: O ■ Example: Suppose A₁ mutates to A2 at rate 0.005, but A₂A2 homozygous recessives are 50% less fit (s = 0.5) than either A₁A1 or A₁A2. What are the expected equilibrial abundances of A₁ and A2? μ = 0.005 S = 0.5 p* = 1-sqrt(µ/s) = 1-sqrt(0.005/0.5) = 0.9 = sqrt(µ/s) = sqrt(0.005/0.5) = 0.1 ● * p = = 1-sqrt(µ/s) q* = sqrt(μ/s) ● Question: Suppose A₁ mutates to A2 at rate 0.01, but A₂A2 homozygous…arrow_forwarda.) If all the blue dots represent FST values between one species in the Americas and one species in Oceania, does this pattern of genetic similarity on the graph suggest that Native Americans and the people of Oceania followed very different migration routes? Why or why not? b.) Given the maximum possible FST value (based on how this statistic is calculated), is it feasible that all human populations have most of the genetic variation within a given population with very little genetic differentiation between any two populations? Give a reason for your answer. c.) Does the graph above suggest that interbreeding during these human contacts had a considerable effect on the gene pools of the two communities? Or is it more likely that only very limited or no interbreeding took place between islanders of Oceania and Native Americans from S. America? Give a reason for your answer.arrow_forwardExplain the role of genetic drift in shaping the genetic landscape of populations. Compare and contrast genetic drift with other evolutionary forces, such as natural selection, highlighting their respective contributions to population genetic variation.arrow_forward
- In many large mammal populations, highways can be barriers to movement - individuals rarely cross them. One solution to this problem has been to install overhead bridges for wildlife to safely cross. The goal is to increase gene flow between the populations on either side of the highway. Which of the following would you expect to see if the bridge is successful in its goal? O Higher levels of drift would occur after the bridge is installed The two populations would have different mutation rates O Both populations would decrease in size O The two populations would become more genetically similar O We would see fewer heterozygotes in both populationsarrow_forwardFitness is, most correctly, a technical term.What does it mean? What two things do u suppose govern the rate of evolution by natural selection? Explain how Darwinian evolution can decrease and increase the frequency of an allele (or a more complex heritable trait, for that matter).arrow_forwardDefine genetic drift and give three ways in which it can arise. Whateffect does genetic drift have on a population?arrow_forward
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