Question

Both the husband and wife have normal vision. The wife gives birth to a colour-blind daughter. Is it more likely that the father is colour blind or has normal vision? What does this lead you to deduce about the girl’s parents genome?

Answer 1

The colour blindness gene is carried on the X chromosome. As a result, as a daughter is colour blind, she carries two mutant genes associated with the blindness. It means that both parents have the mutant gene. As father has only one X chromosome, he is colour blind.