The diagram shows the results of a breeding experiment using a homozygous black mouse and a white mouse. Mouse 1 was then allowed to mate with mouse 2. Using C for the dominant allele for coat colour and c for the recessive allele, which answer below correctly identifies the details of their offspring?

Answer:

9) D

We first need to know the genotype of mouse 2.
We know mouse 1 is homozygous dominant, meaning it is CC.
The white mouse must then be homozygous recessive, cc.

C C

c Cc Cc

c Cc Cc

There is a 100% chance that mouse 2’s genotype is Cc.
If mouse 1 and mouse 2 breed, these could be the following genotypes of the offsprings:

C C

C CC CC

c Cc Cc

The offsprings could either be homozygous or heterozygous.
Percentage heterozygous = 50%
Since ‘C’ is the dominant allele and all genotypes contain the C allele. Therefore, all phenotypes would be black only.

So we have 50% heterozygous, black only phenotype and homozygous and heterozygous genotypes. this only corresponds to row D in the question table.