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In rabbits, coat colour is controlled by multiple alleles of a gene. The coat colour of an ordinary wild type rabbit is called agouti, where each coat hair has bands of grey, yellow and black. The allele for agouti is represented by the capital letter C.
Chinchilla rabbits have coats that lack the yellow pigment and therefore the coat appears silver-grey. The allele for chinchilla is represented by CCh.
The Himalayan rabbit coat is white except for black extremities (the nose, ears, feet and tail). The allele for this coat is represented by Ch.
Finally, the albino rabbit lacks pigmentation completely so the coat is completely white and the eyes are pink. Albino is represented by the letter small c.
C is dominant to all other alleles,
CCh is dominant to Ch and c and
Ch is dominant to c.
(i) Table 1 gives the colour phenotypes of four rabbits. On the basis of allele dominance, state all of the possible genotypes for each of the four phenotypes. You should copy out Table 1 into your answers and complete the second column as your answer to this question.
Table 1 Coat colour phenotypes in rabbits.
(ii) Use the problem solving approach shown in Box 8.1 of Book 5 (p. 172) to illustrate a cross between a pure breeding agouti rabbit and a heterozygous Himalayan rabbit. What is/are the expected phenotype/s of the F1 generation and what is the ratio of phenotypes?
(iii) A breeder wishes to cross one of the rabbits from the F1 generation in question
(e)(ii) above with an unrelated agouti rabbit. His intention is to produce a litter where the ratio of agouti to albino offspring is 3:1. What must the genotypes of the two parental rabbits be in order to produce this ratio? Show the genetic cross that you used to obtain your answer.
A complete answer to the questions is provided within an attached Word document. All calculations are included and the logic behind the problems is explained.