A woman with brown eyes and red hair married a man with non-red hair and blue eyes. It is known that the father of the woman had brown eyes, the mother had blue eyes, and both had red hair. The father of the man did not have red hair and blue eyes, the mother had brown eyes and red hair. What are the genotypes of all these people? What can be the eyes and hair of the children of these spouses?
The allelic gene responsible for the manifestation of brown eye color is denoted by A (it is well known that brown eye color dominates blue), and the allelic gene for blue eyes, respectively, will be a. Necessarily the same letter of the alphabet, since this is one sign – eye color. The allelic gene of non-red hair (hair color is the second trait studied) is denoted by B, since it dominates the allele responsible for the manifestation of red hair color – b. The genotype of a woman with brown eyes and red hair, we can write at first incompletely, and so A-bb. But since it is said that her father was brown-eyed with red hair, that is, with the A-bb genotype, and her mother was blue-eyed and also with red hair (aabb), the second allele of a woman with A could only be a, that is, her the genotype will be Aabb. The genotype of a blue-eyed man with non-red hair can first be written as follows: aaB-. But since his mother had red hair, that is, bb, the second allelic gene with B in a man could have only b. Thus, the male genotype is written aaBb. Genotypes of his parents: father – aaB-; mothers – A-bb.
Children from the marriage of the spouses being analyzed will have equally probable genotypes or phenotypes: brown-eyed not red, brown-eyed red, blue-eyed not red, blue-eyed red in the ratio 1: 1: 1: 1.