The schoolboy crossed two black and white hamsters, which gave birth to 12 black hamsters.

The schoolboy crossed two black and white hamsters, which gave birth to 12 black hamsters. When other black and white hamsters were crossed, 6 black and 5 white cubs were born. What are the genotypes of the parents in each cross?

From the results of the first crossing, it follows that the dominant trait (A) is black coat color, and white is recessive (a).

1) In the first case, there is no phenotype cleavage. This happens when monozygotes are crossed for each of the traits, and each forms only one type of gametes.

Parents: AA x aa,

Gametes: A x a,

Offspring: Aa – all black.

2) In the second case, the splitting is approximately 1: 1. This means that one of the parents forms two types of gametes, the second one. Hence, one is heterozygous.

Parents: Aa x a,

Gametes: A, a x a,

Offspring: Aa, aa.