All the offspring of a cross between a black-eyed Mendelian and an orange-eyed Mendelian have black eyes. What is the expected phenotypic ratio of a cross between two orange-eyed Mendelians?
A) 3 black-eyed:1 orange-eyed
B) 0 black-eyed:1 orange-eyed
C) 1 black-eyed:3 orange-eyed
D) 1 black-eyed:0 orange-eyed

Question

Quizplus · Accepted Answer

Since all offspring of a cross between a black-eyed and an orange-eyed Mendelian have black eyes, black eyes are dominant. Two orange-eyed Mendelians are both homozygous recessive, so all their offspring will also be homozygous recessive, displaying the orange-eyed phenotype exclusively.

All the Offspring of a Cross Between a Black-Eyed Mendelian