In humans, the gene for long eyelashes dominates the gene for short eyelashes. A woman with long eyelashes

In humans, the gene for long eyelashes dominates the gene for short eyelashes. A woman with long eyelashes, whose father had short eyelashes, married a man with short eyelashes. What is the probability of having a child with long eyelashes in this family?

Let’s designate the gene that causes long eyelashes as D, and the gene that leads to the development of short eyelashes as d.

The woman’s father had short eyelashes. Let us write its genotype as dd, because for the realization of this trait, the genotype must be homozygous for the gene d. He produced sperm d and passed exclusively the gene for short eyelashes to the offspring.

Consequently, his daughter, who has long eyelashes, is heterozygous – Dd. It produces two types of oocytes – d and D.

Her husband has short eyelashes. Like the woman’s father, he is dd, his sex cells are d.

The offspring possible for a given married couple are represented by the options:

children with long eyelashes (Dd) – 50%;

children with short eyelashes (dd) – 50%.

Answer: 50%.