It is given that one of the parent with a dominant trait have brown eyes and the other parent with a recessive trait has blue eyes. They produce a twin boy with eyes that is blue in color. So the probability of the fraternal twin to transmit his allele of blue eye to his or her offspring is 50 percent.
And also the probability of the offspring to pass the allele on to his or her offspring is 50 %.
The product rule is used : 0.5 x 0.5 = 0.25 or 25%.
