In humans, myopia prevails over normal vision, and brown eyes over blue.

In humans, myopia prevails over normal vision, and brown eyes over blue. The only child of myopic brown-eyed parents has blue eyes and normal vision. Determine the genotypes of all three family members.

Let’s designate the gene that determines the development of myopia in a person as B, then the gene for normal vision will be in.

Let’s designate the gene that determines the brown color of the iris in the human eye as C, then the gene for the blue color of the iris will be c.

A child with blue eyes and normal vision will be bbcc, because homozygosity is a prerequisite for the phenotypic realization of both traits under consideration.

The genotype of a child is formed by the fusion of an egg and a sperm of the type sun, therefore, parents must have the ability to produce such germ cells, which means that they are diheterozygotes.

Let’s write the parents as BbCc, the germ cells produced by them – bc, BC, Bc and bC.

Answer: both parents are diheterozygotes (BbCc), the child is dihomozygotes for genes for recessive traits (bbcc).