Paraphrase answers that correspond with the question except for the one where you have to estimate the equilibrium genotype frequencies from a population with allele frequencies.

After reading sections 16.1 Genes, Population, and Evolution, 16.2 Natural Selection, and 16.3 Maintenance of Diversity, answer the following:

• List the five conditions necessary for Hardy-Weinberg equilibrium and describe what happens to allele frequencies in a population if these conditions are not met.
  • No mutation: no new alleles will be created from mutations
  • No migration: no new members of the population nor their llels will join particular populations, and none leave that population
  • Large gene pool: the population will continue to grow and there may be an increase of allele diversity
  • Random mating: people select mates from random choice, and genotypes or phenotypes do not bias the mate choice
  • No selection: natural selection will not favor one genotype or another, and this could alter allele frequencies.
• Estimate the equilibrium genotype frequencies from a population with allele frequencies p = 0.10, q = 0.9
  • DD: 0.01
  • Dd: 0.018
  • dd: 0.81
• Using Fig. 16.8, on p. 286, describe the three various types of natural selection and what each type produces. Use Fig. 16.10 as an example to show how one of these processes occurs.
  • Stabilizing selection: an intermediate phenotype is the most adaptive for given environmental conditions, and the peak narrows.
  • Directional selection: extreme phenotypes are favored and the distribution curve shifts to one particular extremes (peak shifts).
  • Disruptive selection: two or more extreme phenotypes are favored over the intermediate phenotype, and two peaks result.
• Recognize the difference between a population undergoing stabilizing, directional, or disruptive selection.
  • As mentioned in the previous question, the peak will narrow (stabilizing), shift (directional), or become two peaks (disruptive).
• Explain why sexual selection is a form of natural selection.
  • Sexual selection is a form of natural selection because it enables males and females to adapt for increased abilities in securing mates. The sexual selection could allow for males to have more abilities to compete with other males for a female mates, or females to select a mate with greater fitness. This will increase the female’s own fitness, and since fitness is directly impacted by sexual selection, it is a form of natural selection.
• Identify the ways in which diversity is maintained in a population.
  • Diversity is maintained in a population in one of two ways: natural selection (environment and individuals having specific selecting agents promoting diversity) and the heterozygote advantage (favors heterozygote over two homozygotes to maintain genetic and phenotypic diversity).
• Demonstrate how sickle-cell disease is an example of stabilizing selection. Do the same for cystic fibrosis.
  • Sickle-cell: The genotype Hb^A Hb^S is “favored over the two extreme genotypes,” and the heterozygotes have an advantage since they do not die from getting the disease, nor do they die from malaria, and all alleles are maintained in the population.
  • Cystic fibrosis: The recessive allele will result in a person having defective plasma membrane proteins, and the heterozygote superiority is the factor that contributed to the recessive allele to stay in the population.

Read the section on p. 290-291 Big Idea 1: “Inbreeding in Populations”.

The Hardy Weinberg Equilibrium relies on five conditions to describe an unchanging population. But what happens when these conditions are not met? Answer the following:

• What might have happened to the colorblind allele in the Pingelapese population following the typhoon if Mwanenised had had no children? Only 5 children?
• Would you predict that the Pingelapese population is in Hardy-Weinberg equilibrium? How would you measure this?
  • I would predict that is may not be in the Hardy-Weinberg equilibrium because the allele and genotype frequencies might not stay constant from generation to generation since other evolutionary influences (inbreeding) are present. The Hardy-Weinberg principle requires that mates are chosen at random without preference for a particular trait, and in this case, mates were likely chosen based on the limited amount of choices on the island, and inbreeding is a unique form of nonrandom mating.
• Has the Pingelapese population evolved?
  • The population has evolved because today people can witness the impact of inbreeding on the rate of suffering from colorblindness. One can see that the population, due to its small size and isolated nature, has much higher frequency of achromatopsia.