If someone who is heterozygous for (or a carrier of) a recessive genetic disease has a child with another heterozygous carrier, what are the chances that their child will have (come down with) the disease? (Make an inheritance diagram on scratch paper if it will help you to think this through.)

Question

Quizplus · Accepted Answer

If both parents are carriers of a recessive genetic disease, there is a 25% (or one in four) chance that their child will inherit two copies of the mutated gene and develop the disease. This is because each parent has a 50% chance of passing on the mutated gene to their offspring. When both parents pass on a copy of the mutated gene, the child will have two copies and therefore have the disease. The other three possible outcomes are that the child will not have the disease but will be a carrier like their parents (50% chance) or will not inherit the mutated gene at all (25% chance).

If Someone Who Is Heterozygous for (Or a Carrier Of)