Smooth fur dominates rough fur; black and white fur are incompletely dominant and result in gray.?

Question

A rough gray crossed with a rough gray would produce

A) all rough gray.

B) 1/2 rough black, 1/2 rough white.

C) 1/2 rough black, 1/4 rough gray, 1/4 rough white.

D) 1/4 rough black, 1/2 rough gray, 1/4 rough white.

Answer 1

As both parents are phenotypically rough, and rough is recessive, they both must be homozygous rough.  No smooth alleles to pass on, so ALL offspring must be rough.

As far as coat color, for the parents to be gray, they must each have one black allele and one white allele--heterozygous.  So do the Punnett square for that, using B for black, W for white, and keeping in mind that BW is gray.  [I didn't use the capital and small letters since this is not the usual dominant-recessive case, but rather a case of incomplete dominance.]  You get 1/4 BB (black), 1/2 BW (gray), and 1/4 WW (white).  Remember, they're all going to be rough.

The answer is D.