A dog inherits one gene from each of its parents. The dominant gene gets
expressed in the phenotype. For example, in the B series, a dog can be
genetically black or brown.
Let us assume that one parent is homozygous black (BB), while the other parent
is homozygous brown (bb)
In this case, all the offsprings will be heterozygous (Bb).
Since black (B) is dominant, all the offsprings will be black. However, they
will have both B and b alleles.
If such heterozygous pups are crossed, they will produce 25% homozygous black
(BB), 50% heterozygous black (Bb), and 25% homozygous brown (bb) offsprings.