Monohybrid cross in mice
A coat colour locus (B) in mice influences black or
brown fur. Each Bb parent
produces equal numbers of B
and b gametes.
Random union of B
and b gametes
produces four possible combination, BB, Bb , bB,
and bb, at equal
frequencies, of which three (BB, Bb, and bB) produce black
offspring due to the dominance of B to b,
and one (bb)
produces a brown offspring. Thus the mating of two
heterozygous black
mice produces an expected ratio of 3 black : 1 brown
offspring.