If both parents are carriers of a recessive disease allele, what is the chance that one of their unaffected children is also a carrier?

Question

Quizplus · Accepted Answer

When both parents are carriers of a recessive disease allele, their children have a 25% chance of being affected (having the disease), a 50% chance of being carriers (having one copy of the disease allele but not affected), and a 25% chance of not having the disease allele at all. For an unaffected child, the possibilities of being a carrier or not having the disease allele are the only outcomes, making the probability of being a carrier 2/3 when excluding the affected (25%) outcome.

If Both Parents Are Carriers of a Recessive Disease Allele