University of London

(University College London)

BSc Degree 1998

GENETICS B7: POPULATION AND EVOLUTIONARY GENETICS

Answer ONE question from section A, TWO questions from section B, and ALL OF section C (overleaf). Each section carries 1/3 of the marks on the paper.

Section A. Answer ONE of questions 1-3.

1. Discuss the various interpretations of evolutionary change seen in the fossil record. Illustrate your review with two examples.

2. How can phylogenetic approaches be used to determine the origins of species? Review the assumptions of different methods of phylogeny reconstruction.

3. Discuss the relative importance of reinforcement, sexual selection, and post-mating isolation in speciation.

Section B. Answer TWO of questions 4-8.

4. "Evolutionary adaptations inevitably result from the accumulation of many mutations of individually small effect on the phenotype". Is this true or false? Support your answer with examples.

5. Summarize the ways in which natural selection can act upon quantitative variation. Give details of an example of each mode, and describe the possible effects on the level of genetic variation in such traits.

6. Are transposable elements important in evolutionary processes? Illustrate your argument with examples.

7. How can theories of clines and hybrid zones explain the maintenance of genetic variation across geographic areas? Give examples.

8. Give three major ways in which female choice may explain the evolution of secondary sexual characteristics. Give a brief example of each.

Remember to answer Section C overleaf!

Section C. Answer all parts of question 9, even if you cannot do an earlier part.

9. The MN blood group system is inherited as a single codominant, autosomal locus. In Hokkaido, Japan, the following genotypic data were obtained:

          L^ML^M      L^ML^N      L^NL^N       Total

          406       744       332       1482

a) Estimate the allele frequencies, (p, q, respectively) for L^M and L^N.

b) Calculate the expected frequencies (P, Q, and R, respectively) for the three genotypes under random mating. From these frequencies, calculate expected numbers.

c) Use a chi-square test to find whether there is evidence for deviation from Hardy-Weinberg. Apart from selection, suggest three reasons why genotypes might not be in Hardy-Weinberg equilibrium.

d) Survival from birth is very similar between genotypes. Suppose, however, these blood groups are actually under very strong selection, with heterozygote women on average twice as fertile as homozygotes. Can you tell whether this is supported or denied by the data above? (Note: under random mating and equal genotypic fertility, L^ML^M female x L^ML^N male matings, for example, should occur with frequency of PQ, resulting in 0.5 PQ L^ML^M offspring and 0.5 PQ L^ML^N offspring from this mating type in the next generation).

e) If heterozygote women were twice as fertile, what would be the expected direction of evolution of gene frequencies?

End of paper