Jermaine and Shikia are healthy parents of three young children.The oldest two,Bethany and Amber,are healthy,and they are six and four,respectively.Their youngest child was born with Peeling Skin Syndrome two years ago.Roscoe's skin constantly peels,and is red and itchy.If Jermaine and Shikia have another child,the probability that he or she will inherit the skin condition is

Question

Quizplus · Accepted Answer

Peeling Skin Syndrome is a rare genetic disorder caused by mutations in the genes responsible for the structure and maintenance of the skin. Since their youngest child has the condition, we know that both Jermaine and Shikia carry at least one copy of the mutated gene. 
When two carriers of a rare genetic condition have children, there is a 25% chance for each child to inherit two copies of the mutated gene and therefore have the condition, a 50% chance to inherit one mutated gene and be a carrier like their parents, and a 25% chance to inherit two normal copies of the gene and not be affected. 
So the probability that their next child will inherit Peeling Skin Syndrome is 1/4 or 25%.

Jermaine and Shikia Are Healthy Parents of Three Young Children