Genetics: Interactions of genes at multiple loci?

Let B = Brown and b = yellow (since B is dominant and b is recessive)

First cross with yellow female with brown male produced

1/2 BB or Bb (could be either since the brown offsprings could have been heterozygous)

1/2 bb (has be to so because yellow alleles are recessive)

Second cross with yellow female and brown male produced

Bb (cannot be BB since the female does not have a B allele)

Therefore, we know that the first brown male dog was heterozygous. If the first dog was homozygous, the cross would not have been able to produce any yellow offspring.

Here yellow coluor is recessive and brown is dominant. so lets assume that a yellow female has a genotype yy.

In first case, the genotype of male would be Yy (brown colour), so after mating

yy X Yy

the genotype of offsprings would be Yy (brown), Yy (brown), yy (yellow), yy (yellow). so 50% offsprings are yellow and 50% are brown.

In second casr, the genotype of brown male would be YY (homozygous dominant), so after mating

yy X YY

the genotype of offsprings would be Yy (brown), Yy (brown), Yy (brown), Yy (brown). so all are brown

Good job. *Its = the ongoing search of its causes (...)