Genetics: Analysis and Principles 5th Edition by Robert Brooker

Exercise 2

Identical twins are produced from the same sperm and egg (which splits after the first mitotic division), whereas fraternal twins are produced from separate sperm and separate egg cells. If two parents with brown eyes (a dominant trait) produce one twin boy with blue eyes, what are the following probabilities
a. If the other twin is identical, he will have blue eyes
b. If the other twin is fraternal, he or she will have blue eyes
c. If the other twin is fraternal, he or she will transmit the blue eye allele to his or her offspring
d. The parents are both heterozygotes.