Two gray rats were crossed with a white male. In the offspring of the first female – 7 gray cubs, in the offspring of the second – 5 white and 4 gray. What coat color dominates? Record both crosses.
– As a result of the first crossing, a uniform offspring was obtained – all cubs are gray. Based on Mendel’s first law, it can be concluded that both parents were homozygous, with the gray color of the coat dominating the white.
– We introduce the notation of genes:
A – gray wool;
and – white wool.
Therefore, the genotype of the first female is AA, the genotype of the male is aa.
– The second female has gray hair. However, it cannot be homozygous, because In the offspring, 1: 1 phenotype cleavage is observed (5 white cubs and 4 gray). So, the second female is heterozygous, her genotype is Aa.
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