Question

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.

Answer 1

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

Answer 2

1/2 black, 1/2 white