In humans, brown eyes dominate blue ones, and the ability to write with the right hand over left-handedness.

In humans, brown eyes dominate blue ones, and the ability to write with the right hand over left-handedness. The genes that control these traits are located on different chromosomes. what is the probability of the birth of a crooked-eyed left-hander in a family where both parents are heterozygous.

Let’s designate the gene that causes the development of brown-eyed as B, then the gene that leads, in a homozygous variant, to the development of a blue iris will be b.

Let’s designate the gene that determines the dominance of the right hand and the corresponding hemisphere as C, then the gene for left-handedness will be c.

Parents, according to the condition of the problem, are heterozygotes – BbCc. Both of them produce the following types of germ cells: BC, bc, Bc and bC.

Among the offspring of this pair, the following gene and phenotypic variants are possible:

brown-eyed right-handed children (ВВСС, 4 ВbСс, 2 ВbСС, 2 BBCc);

blue-eyed left-handed children (bbcc);

blue-eyed right-handed children (2 bbСс, bbСС);

brown-eyed left-handed children (2 BBcc, Bbcc).

Having solved the arithmetic problem, we determine the probability of the birth of a brown-eyed left-hander in a given parental couple:

(3 * 100) / 16 = 18.75%.