Question

In humans, brown eyes are dominant to blue eyes. How could two parents with brown eyes have a son with blue eyes?

Answer 1

both of the parents would have to have the blue eye gene

Answer 2

Someone with broken OCA2 genes will have blue eyes no matter what the HERC2 genes are. ... Because the two genes depend on each other, it is possible for someone to actually be a carrier of a dominant trait like brown eyes. And if two blue eyed parents are carriers, then they can have a brown eyed child.