Human Sciences Final Honour School: Paper 2
HUMAN GENETICS AND EVOLUTION
I.
Human Population Genetics
Website: http://www.human-sciences.ox.ac.uk/teaching/
http://www.stats.ox.ac.uk/~harding
Revision exercise for lectures 1 to 3.
1. Consider a hypothetical population in which you find 32.5% of the individuals to be
homozygous rr at the MC1R locus (phenotype: red hair). If the population is in HardyWeinberg equilibrium, and there are two common alleles at this locus (r and R), what are
the other genotype proportions?
2. About 90% of a population are tongue curlers; the allele for tongue curling is dominant.
What do you expect for the gene frequencies T and t, and for the genotype proportions?
3. Observe the following hypothetical populations:
Genotypes
Population
DD Dd dd
1.
200 600 200
2.
0 1000
0
3.
498
4 498
4.
250 500 250
(a) What are the gene frequencies of each of these populations?
(b) Which of these populations, if any, is in Hardy-Weinberg equilibrium?
(c) Assuming that no forces exist which would disturb these populations and that random
mating now occurs, what will be the genotype frequencies among the progeny of the
next generation in each population?
4. Calculate the inbreeding coefficient, FK, for first cousins once removed. Draw the
pedigree.
5. In a population of 100 couples, 5 couples are first cousins, seven are second cousins, and
the rest are unrelated (FK=0). Calculate the average inbreeding coefficient for this
population. (Note that the average inbreeding coefficient in human populations is
generally around 1 per 1000, i.e. 0.001, but more than ten-fold higher in some isolates, eg
Hutterites, Samaritans, Tristan da Cunha.)