Answer:
See the answer below
Step-by-step explanation:
Let us assume that the gray color in mice is represented by the G allele and the white color is represented by g allele. For a cross between a homzygous gray mouse and a white mouse:
Genotype of the gray mouse - GG
Genotype of the white mouse - gg
Crossing the two parents
GG x gg
F1 Gg Gg Gg Gg
All (100%) the offspring at the F1 would have the genotype Gg and would be gray in color since G is dominant over g. (See the attached image for the Punnet's square).