Phenylketonuria a metabolic disease in humans is caused by a

Phenylketonuria, a metabolic disease in humans, is caused by a recessive allele, k. If two heterozygous carriers of the allele marry and plan a family of five children, what is the chance that at least three children will be unaffected? SHOW YOUR CALCULATIONS!

Solution

at least three children will be unaffected. so, probability is

xxxyy (5!/3!2!)=10

xxxxy (5!/4!1!)=5

xxxxx(5!/5!) =1 (Let here x , y be affected and unaffected children)

these are the chances