In mice, a gene controlling coat colour has 2 alleles; B (black) and b (white). A pure breeding black mouse is crossed to a white mouse and all the offspring are black. The offspring are then crossed to white mice. The phenotypes of the offspring of this second cross are expected to be

all black.
1/4 black, 3/4 white.
all white.
1/2 black, 1/2 white.
3/4 black, 1/4 white.

2 answers

The mice would be half heterozygous for black, and half white.
1/2 black, 1/2 white