In humans, blue eyes are inherited as a recessive autosomal trait and colour blindness is an X- linked recessive trait. A woman with blue eyes and normal colour vision whose father was colour blind marries a man who also has normal colour vision. He has brown eyes but his mother had blue eyes. Which of the following do you expect to be true for their daughters?

Question

Quizplus · Accepted Answer

Blue eyes are recessive, so the woman with blue eyes must have two copies of the blue eye allele. Her father was color blind, so he must have had one copy of the X-linked color blindness allele, which he passed on to his daughter. The man with brown eyes could either have two copies of the brown eye allele or one copy of the brown eye allele and one copy of the blue eye allele. His mother had blue eyes, so he must have received a blue eye allele from her. 
Therefore, the possible genotypes for the parents are:
Woman: bb XBXb
Man: BB or Bb XbB or XbXb
When you combine these genotypes to predict the genotypes and phenotypes of their daughters, you get the following:
50% chance of BB or Bb and XBXb → Normal color vision, brown eyes
50% chance of Bb and XbXb → Normal color vision, blue eyes

In Humans, Blue Eyes Are Inherited as a Recessive Autosomal