Question 1: White Leghorn chickens are homozygous for a dominant allele, C, of a gene responsible for coloured feathers, and also for a dominant allele I, of an independently segregating gene that prevents the expression of C. The White Wyandotte breed of chickens is homozygous recessive for both genes, c/c,i/i. What proportion of the F2 progeny obtained from mating White Leghorn X White Wyandotte
would be expected to have coloured feathers? SCHOOL OF APPLIED SCIENCES
Question 2: Seborrheic keratosis is a rare hereditary skin condition due to an autosomal dominant mutation. Affected people have skin marked with numerous small sharply margined, yellowish or brownish areas covered with a thin greasy scale. A man with keratosis marries a normal woman and they have three children.
a. What is the chance that all three are normal?
b. What is the chance that all three are affected?
Question 3: Plumage in ducks is determined to some extent by a series of multiple alleles named restricted (MR = white on the wing fronts), mallard (M = wild type), and dusky (md = darker plumage). MR is dominant to M, which is dominant to md
(i) Can the mating between two mallard ducks produce any offspring with restricted plummage? Explain.
(ii) A series of matings between two mallard ducks produced the following offspring: 34 mallard and 11 dusky ducks. What are the likely genotypes of the two mallard parents?
(iii) Can a mating between two ducks with restricted plumage produce offspring with dusky plumage? Explain using diagrams of appropriate matings.