1.   a)Two individuals from a large population o...

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1.   a)Two individuals from a large population of birds colonize an island, and the populationquickly rises to about 50 breeding pairs for the next 10 years. Assuming these birdsbreed once per year, and live for one year on average, estimate the average effectivepopulation size since colonization. What have you assumed?
b)If the average neutral site heterozygosity in the large population of birds was 0.01, whatheterozygosity is expected 10 years after the bottleneck associated with colonization of the island?
c)If a new, semi-dominant mutation of selective advantage 0.01 in heterozygotes arose in the island population, what would the fixation probability of this mutation be, relative to that of a newly arisen neutral mutation, assuming the actual and effective population sizes remain at 100 in the long term?

2   a)In a very large population of Anopheles gambiae 20 new mutations haveappeared which confer DDT resistance. Each of these confers a 2.5% advantage toits (heterozygous) bearer. What is the probability that at least one of these mutations will survive to reach an appreciable frequency?
b)After some time a DDT resistant mutation has reached a frequency of 1% in the population, how much longer would it take to reach a frequency of 50% if it has additive effects on fitness?
c)How much would mean fitness increase by over this period?
d)At what allele frequency do you see the most rapid evolutionary change in allele frequency and why?
e)Once the frequency of the DDT resistant mutation had reached 50%, DDT use wasdiscontinued. Under these conditions the resistant mutation has the same fitness as the wild-type when heterozygous, but has a 5% disadvantage when homozygous. By how much has the marginal fitness of the resistant mutation changed by?

3   Huntington's disease is a genetic disease in humans, and the disease causing allele is at a frequency of 0.00025.
a)Assuming the human population is large and randomly mating, and assuming theallele is not completely recessive and its frequency is at mutation-selection equilibrium,determine the fitness of the heterozygote relative to the wild-type homozygote assumingthat the mutation rate to the disease causing allele is 10-8
b)If the disease allele was homozygous lethal what would the mean fitness be
c)What is the mutation load caused by this allele, and explain why this is the case
d)If there were 10 loci in the human genome all of which had the same properties asthe Huntington locus what would their contribution to the mutational load be if there wasno epistasis?
e)If humans were suddenly made to in breed at a rate 0.5,by how much would the mutation load change by, and why?

4   The butterfly Heliconius melpomene carries a bright warning pattern, which advertises its distastefulness to predators. Two geographic races, which carry different colour patterns, meet near Tarapoto in Peru. These pattern differences involve two genes, and genotypes can be scored by examining the patterns of wild-caught individuals. However, each gene shows complete dominance, and so not all genotypes can be distinguished. One race carries alleles D, N at the two loci, respectively, and the other carries alleles d, n, where the dominant alleles at each locus are designated by upper-case letters. A sample of 48 butterflies was taken from a population near the boundary, and scored as follows:

                   DD or Dd       dd
NN or Nn    25                   5
Nn               8                   10

a)Is there a significant association between the genotypes at each locus?
b)Assuming Hardy-Weinberg proportions at each locus, estimate the allele frequenciesfor each locus.
c)Making the same assumption, find the frequencies of gametes carrying recessive alleles at both loci.
d)Hence, find the coefficient of linkage disequilibrium and correlation coefficient between the two loci.

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Answer 1a: In the question given that two individuals (Nf: 1 female; Nm: 1 male) from a large population of birds colonize an island, and the population quickly rises to about 50 breeding pairs for the next ten years. As not all individuals reproduce in the population and therefore we have assumed that these birds breed produce gametes once per year producing potential offspring and live for one year on average.
The effective population size depends on the sex ratio and the reproduction mechanism.
For the first year, Ne was 2, but as per assumption equal number of birth and death rate and due to a large population to which birds belong, the Ne was larger than the initial individuals. Because the number of individuals produced in every generation for 10 years was larger than the previous one. According to census count of the population (P) given 50, the average effective population is 50 for an equal number of female and male birds. Else for unequal sex ratio, the effective population would have been lesser than P, may be 20...

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