Imagine that a newly discovered species of fish normally has three eyes (E), but the rare mutation (e)causes "diopthalmic" fish with two eyes to be born. In addition, eye color in these fish is inherited similarly to humans, with black eyes (B)being dominant to blue (b). Assuming these two genes are carried on separate chromosomes, what must the genotypes of two black-eyed, three-eyed parents be if they have a blue-eyed, diopthalmic son?

Question

Quizplus · Accepted Answer

Since the parents are both black-eyed, they must be either homozygous dominant (EEBB) or heterozygous (EeBb) for the eye color gene.

The fact that they have a diopthalmic son means that both parents must be carriers of the recessive mutation (e), so their genotypes for the three-eyed gene must be Ee.

We know that their son has blue eyes, so he must be homozygous recessive (bb) for the eye color gene.

Therefore, the most likely genotype for the parents is EeBb, which would give a 25% chance for a diopthalmic, blue-eyed offspring.

Imagine That a Newly Discovered Species of Fish Normally Has