Answer:
All white offspring: Parent 1 genotype = homozygous dominant
Parent 2 genotype = homozygous/heterozygous dominant
For all black offspring: Parent 1 genotype = homozygous recessive
Parent 2 genotype = homozygous recessive
Explanation:
The cross was between a white mouse and a black mouse and the phenotypic ratio of the resulting offspring is 50% white and 50% black.
Assuming that fur color in the mouse is represented by the allele A (a), In order to give 1:1 phenotypic ratio of the offspring, it means the white mouse is heterozygous with Aa genotype and the black mouse is homozygous with aa genotype. Also, it means that the allele A is dominant over the allele a.
Aa x aa
Aa Aa aa aa
Aa = white
aa = black
Ratio of white to black = 50/50 or 1:1
Hence, in order for a cross to yield only white offspring, the parents can either be homozygous AA and AA or one will be homozygous AA and the other will be heterozygous Aa.
1. AA x AA
AA AA AA AA (all white offspring)
2. AA x Aa
AA Aa AA Aa (all white offspring).
In order to produce only black offspring, both parents must be homozygous aa.
aa x aa
aa aa aa aa (all black offspring)
