Coat colour in mice is controlled by two genes, each with two alleles. The genes are on
different chromosomes.
One gene controls the pigment colour. The presence of allele A results in a yellow and black
banding pattern on individual hairs, producing an overall grey appearance called agouti. Mice with
the genotype aa do not make the yellow pigment and are, therefore, black.
The other gene determines whether any pigment is produced. The allele D is required for
development of coat colour. Mice with the genotype dd produce no pigment and are called
albino.
Question : Give all the possible genotypes for a black mouse.
I don't know how to work this out