Suppose a BB female mouse mates with a Bb male mouse. Which of the following represents the probabilities of each genotype occurring among their offspring?

As the offspring inherits one allele from each parent, it will obtain only the B allele from the female mouse and either the B or b allele from the male mouse. Hence possible offspring genotypes are BB or Bb with 0.50 probability each (each probability of either genotypes being present in the offspring).