A pure breeding male black dog is mated with a female brown bitch and they produce a litter of 12. The allele for black fur is dominant to the allele for brown fur. What is the expected distribution of colour and sex in their litter?

This is the correct answer. The pure breeding male’s genome must be BB and the brown bitch’s genome must be bb. The allele for black fur is dominant over the brown allele. Therefore, all the offsprings will be black (Bb). The dog carries the X and Y chromosomes. The bitch carries two X chromosomes. At meiosis, only one of each chromosome pairs goes to the gametes.