Question

A rabbit breeder wishing to breed only black-haired rabbits wants to know if the black rabbit it has carries the recessive allele for white fur. Both of the rabbit's parents had black fur.
Which of the following methods would be the best method for the breeder to use in order to determine if the rabbit will produce pure-breeding black-haired offspring?

• A. Cross-breed the rabbit back to its parents and see if any offspring have white fur.
• B. Breed the rabbit with another rabbit with black fur and see if any of the offspring have white fur.
• C. Examine the chromosomes from a hair cell from a black hair on the rabbit.
• D. Closely examine the rabbit's fur to see if there are any white hairs embedded within.
• E. Cross-breed the rabbit with a rabbit that has white fur, if the offspring are all black, the rabbit is pure breeding for black fur.

Answer 1

Answer: (E)

Cross-breed the rabbit with a rabbit that has white fur, if the offspring are all black, the rabbit is pure breeding for black fur.

The breeder should cross breed the rabbit with a rabbit that has white fur. If the rabbit is homozygous for black fur then all the F1 hybrids will be black and if the rabbit is heterozygous for black fur then half of the F1 hybrids will be black and half of F1 hybrids will be white. This can be demonstrated by the cross as shown in the figure.

So, the correct answer is 'Cross-breed the rabbit with a rabbit that has white fur, if the offspring are all black, the rabbit is pure breeding for black fur'.