The original source of new alleles, upon which selection operates,is mutation, a random event that occurs without regard to selectionalvalue in the organism. Although many model organismshave been used to study mutational events in populations, someinvestigators have developed abiotic molecular models. Soll et al.(2006. Genetics 175:267–275) examined one such model to studythe relationship between both deleterious and advantageousmutations and population size in a ligase molecule composed ofRNA (a ribozyme). Soll found that the smaller the population ofmolecules, the more likely it was that not only deleterious mutationsbut also advantageous mutations would disappear. Whywould population size influence the survival of both types ofmutations (deleterious and advantageous) in populations?

The original source of new alleles, upon which selection operates,is mutation, a random event that occurs without regard to selectionalvalue in the organism. Although many model organismshave been used to study mutational events in populations, someinvestigators have developed abiotic molecular models. Soll et al.(2006. Genetics 175:267–275) examined one such model to studythe relationship between both deleterious and advantageousmutations and population size in a ligase molecule composed ofRNA (a ribozyme). Soll found that the smaller the population ofmolecules, the more likely it was that not only deleterious mutationsbut also advantageous mutations would disappear. Whywould population size influence the survival of both types ofmutations (deleterious and advantageous) in populations?

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter10: From Proteins To Phenotypes

Section: Chapter Questions

Problem 23QP

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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.
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?
Small population size causes genetic drift because ofchance sampling of different alleles from one generation to the next. We can predict how much geneticdrift occurs for a given population size using binomialsampling statistics. With a population of size N, wecan estimate that 95% of the time the allele frequency(p) in the next generation will be withinthe confidence interval of p ± 1.96 (√p(1 − p)2N ),where p(1 − p)2Nis an estimate of the statistical variancein allele frequencies from one generation to the nextwith random sampling of 2N alleles each generation. a. What is the confidence interval for p = 0.5 whenN = 100,000?b. What is the confidence interval for p = 0.5 whenN = 10?c. How are the results in parts (a) and (b) related tothe consequences of a population bottleneck?
The sd gene causes a lethal disease of infancy in humanswhen homozygous. One in 100,000 newborns die eachyear of this disease. The mutation rate from Sd to sd is2 × 10−4. What must the fitness of the heterozygote be toexplain the observed gene frequency in view of the mutation rate? Assign a relative fitness of 1.0 to Sd /Sd homozygotes. Assume that the population is at equilibriumwith respect to the frequency of sd.
A/A and A/a individuals are equally fertile. If 0.1 percent of the population is a /a, what selection pressureexists against a /a if the A → a mutation rate is 10−5 ?Assume that the frequencies of the alleles are at theirequilibrium values.
Natural selection tends to work toward genetic unity;the genotypes that are most fit produce the mostoffspring and increase the frequency of adaptive allelesin the population. Yet there remains a great deal ofvariability within the populations of species. Describethe factors that contribute to this genetic variability. Provide the link of references
Consider the first copy of an allele for insecticideresistance that arises by mutation in a populationof insects exposed to an insecticide. Is this mutation an adaptation? If, after some generations,we find that most of the population is resistant,is the resistance an adaptation? If we discovergenetic variation for insecticide resistance in apopulation that has had no experience of insecticides, is the variation an adaptation? If an insectpopulation is polymorphic for two alleles, eachof which confers resistance against one of twopesticides that are alternately applied, is thevariation an adaptation? Or is each of the tworesistance traits an adaptation?
In a particular population of mice, certain individualsdisplay a phenotype called short tail, which is inherited as a dominant trait. Some individuals display arecessive trait called dilute, which affects coat color.Which of these traits would be easier to eliminatefrom the population by selective breeding? Why?
Microevolution is defined as a change inallele frequencies in a population over generations. Please explainwhat an allele is, in genetic terms. Name the three major factorsinvolved in allele frequency changes in populations. Describe, indetail, how natural selection works on individuals, while evolutionoccurs in populations. Include a real or hypothetical example ofthe process of natural selection in your answer other thaninsects and insecticide! Identify the specific natural selectionpressure and the specific trait being selected for in yourexample.
For a locus with two alleles (B and b) in a population at riskfrom an infectious neurodegenerative disease, 16 individualshave the genotype BB, 92 individuals have Bb and 12individuals have bb. Use the Hardy-Weinberg equation todetermine whether this population appears to be evolving.
What is Darwinian fitness? What types of characteristics canpromote high fitness values? Give several examples.
Entomologists at the New York State Department of Agriculture are interested in determiningthe connection between pest insects infesting crop plants with populations of the same insectinfesting native plants in natural habitats. Long term trapping and monitoring studies haveestimated that on average 3% of the populations move between habitats (farm to natural and visversa) each generation. A new insecticide resistance allele (∆K) has begun to increase infrequency in the agricultural populations. A genotyping survey at this locus of 50 individuals ineach population has revealed the following genotype counts: K/K K/∆K ∆K/∆K Agricultural field 32 16 2 Forest 48 2 0 4a. Based on the effects of migration alone, what will the frequency of ∆K be in the forestpopulation in the next generation? 4b. If migration was acting in here without selection, what would the frequency of ΔK be in theagricultural population in the next generation? 4c. If the natural forest population was…