University of London

(University College London)

BSc Degree 1995

GENETICS B7: POPULATION AND EVOLUTIONARY GENETICS
 

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

Section A. Answer ONE of questions 1-3.

1. How does genetic drift interact with selection in (a) chromosomal evolution OR (b) molecular evolution OR (c) survival of endangered populations?

2. How can phylogeny reconstruction and knowledge of distribution patterns help in understanding the origins of species?

3. How might kin recognition and associations between kin affect the evolution of behaviour?

Section B. Answer TWO of questions 4-8.

4. What are meant by stabilising selection, disruptive selection and directional selection? Describe one example of each from a natural population.

5. "Evolutionary rates are not controlled by mutation rates". Discuss.

6. How do we study the inheritance and evolution of quantitative traits?

7. Are genes of major effect important in evolution?

8. What factors affect whether gametic disequilibria build up? Give examples.
 

Remember to answer Section C overleaf!

Section C. Answer ONE of questions 9-10.

9. In a population of the vermilion tiger moth, which is warningly coloured and unpalatable to predators, there are three morphs inherited at a single gene, B: a melanic morph, with genotype BB, an intermediate, Bb, and the normal vermilion morph, bb. 45 melanics, 555 intermediates, and 6538 vermilions were captured from a single, large population.

a) Estimate the frequencies, p and q of the alleles B and b.

b) What are the expected numbers of genotypes given random mating? Do the observed numbers of genotypes differ significantly from those expected?

c) Estimate the deviation, F, from Hardy-Weinberg ratios [remember that the frequency of heterozygotes = 2pq(1-F)]. What processes might lead to this kind of deviation?

d) Lab. studies showed that mating was disassortative, i.e. unlike genotypes tended to pair together. How should this affect genotype freqencies?

e) If disassortative mating occurs in the wild, as well as in the lab., how would this affect your answer in (c) above?

f) How might selection for warning colour affect the gene frequencies?

10. A subspecies of the white panther from Louisiana (Felis albabayouensis) was recently described on the basis of black toes (rare in other subspecies, but found in all bayouensis), unusual tufts of hair on its nape and a bend in the tip of the tail. Only about 60 individuals of the new subspecies remain in the wild. Thirty-five individuals were sampled for 42 enzyme loci using starch gel electrophoresis; of these only one, phosphoglucomutase (Pgm) was polymorphic. At Pgm there were two alleles; fast (F) and slow (S). The numbers of each genotype at Pgm were as follows: FF 11, FS 20, SS 4.

a) Estimate the frequencies of alleles at Pgm.

b) What are the expected numbers of genotypes given random mating? Do the observed numbers of genotypes differ significantly from those expected?

c) What is the "expected heterozygosity" (proportion of heterozygotes expected) at Pgm?

d) What is the average expected heterozygosity over all 42 loci?

e) At these same 42 loci, other subspecies of white panther have average heterozygosities of around 10%. What might explain the differences?

f) What advice would you give conservation managers about this subspecies? If later work showed an unusually high level of spontaneous abortion and juvenile mortality in this subspecies, how would this affect your opinion of conservation possibilities?