In rabbits, assume that the dominant allele ( B ) produces black fur. The allele

Question

In rabbits, assume that the dominant allele (B) produces black fur. The allele (b) for white fur is recessive to B.

(a) What colour fur will each of the following rabbits have?

                    Rabbit 1           Rabbit 2         Rabbit 3         Rabbit 4

genotype       BB                    Bb                  bB                   bb

   (b) Which of them will breed true?

   (c) Which rabbits are homozygous for coat colour?

   (d) If rabbits 1 and 4 were mated together and had 12 babies, how many of these would you expect to be black?

   (e) If rabbits 2 and 3 are interbred and produce several litters, totalling 48 babies, how many white babies would be predicted by the laws of genetics?

   (f) If rabbits 3 and 4 are mated together on several occasions and have 50 babies altogether, how many of their babies would you 'expect' to be black?

Explanation / Answer

(a) Rabbit 1 (BB) will be black; Rabbits 2 and 3 (Bb or bB) will be black; Rabbit 4 (bb) will be white.

   (b) Rabbits 1 (BB) and 4 (bb) will breed true.

   (c) Rabbits 1 (BB) and 4 (bb) are homozygous for coat colour.

   (d) All 12 babies should be black as rabbit 1 contributes dominant alleles to all the offspring.

   (e) If the heterozygous rabbits (Bb) are mated, you would expect a ratio approximating to 3 black to 1white baby; e.g. 36 black and 12 white.

   (f) Rabbit 4 contributes only recessive alleles so approximately 50% of the babies should be black and 50% should be white; e.g. 25 of each.

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