Answer to Question #162286 in Biology for Anas Bajbouj

Question

Solve the problem: Unicornism is an X linked recessive trait. A normal man marries a normal woman and they have many children. 

 

They have normal and unicorned boys, and all the girls are normal.

 

Using a punnet square and also showing the genotypes of the parents and children explain how this can happen .

Answer 1

Let's consider that d is a disease allele while D is a normal allele. Only individuals with two disease alleles have unicornism. Since the parents have a son with the disease and are healthy, it can be suggested that the mother is a carrier of the disease allele d. From here, the genotypes of parents and their gametes are:

Male: X^DY; gametes - X^D and Y;

Female: X^DX^d; gametes - X^D and X^d.

From here, the genotypes of their children are: