Lecture 40: Population genetics II

Pick up eugenics questions from lecture 14, 1997 questions. They did not get transferred during revision of new lecture 9 questions.

1. What possible explanations can be offered for loss of heterozygosity in certain populations found in the wild?

2. What criteria must be met for a genetic locus to be considered monomorphic? Polymorphic?

3. What is meant by the term "bottleneck" as it is used in genetics?

4. The Northern elephant seal has made a substantial recovery from near extinction. Why are geneticists still worried about its future?

5. Why is a high level of polymorphism in a population considered desirable?

6. What driving forces have caused the allelic frequency of Hb^S, which causes sickle cell anemia when it is homozygous, to become elevated in Central African populations?

7. What is the relationship between relative fitness and selection coefficient?

8. What is heterozygous advantage and what impact does it have on the population that emerges from an extended selective process?

9. In a population in which there is heterozygous advantage, what determines which of the two alleles that are involved reaches the highest equilibrium frequency? (You may have to make a common-sense extension from what has been presented to answer this one. Think in terms of the relative s values for the two homozygotes.).

10. Why does an allele that provides resistance to an adverse environmental condition not always become fully established and essentially monomorphic in a population?

11. Explain how a balance between selection and mutation can establish a constant allelic frequency for a recessive lethal trait.

12. Describe two different ways in which reduction of a population to a small size can permanently alter the genetic composition of the progeny of that population, even if their number later increases.

13. What are the mechanisms responsible for genetic drift, and how do they differ from founder effects?

14. Explain how an environmental change can alter selection. Illustrate with a real-life example.

15. What is meant by the concept of heritability when it is applied to a phenotypic trait that is influenced by polygenic inheritance? (You may need to go back to Lecture 9 notes for this one).

16. What is the current concensus view on the extent of heritability of human intelligence?

17. Why may it not be valid to assume, based on the heritability of human intelligence, that a large fraction of observed differences in IQ scores between ethnic groups is inherited?

18. Why is it valuable to have a high degree of heterozygosity in a population?

19. What was the stated goal of the eugenics movement in the United States? What measures were undertaken to achieve those goals? What scientific considerations caused leading genetics to oppose the eugenics movement?

20. Why is sterilization of homozygous afflicted individuals not a very effective means of eliminating relatively rare genetic defects?

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