Question

A genetic counselor meets with a couple who are both carriers for a recessive genetic condition. They want to understand the probability that their children will be affected. Using Mendelian genetics principles, what can the counselor tell them about inheritance probabilities?
Question 8 options:

Each child has a 25% chance of being affected, 50% chance of being a carrier, and 25% chance of having two normal alleles

No children will be affected, but all will be carriers like their parents

The inheritance pattern is too complex to predict without extensive genetic testing

All children will definitely be affected because both parents carry the recessive allele

Answer 1

Correct answer: Each child has a 25% chance of being affected, 50% chance of being a carrier, and 25% chance of having two normal alleles.

Why: If both parents are heterozygous carriers (genotype Aa) for an autosomal recessive condition, a Punnett square gives offspring genotypes of AA, Aa, Aa, aa. That yields 25% AA (unaffected, non‑carrier), 50% Aa (unaffected carrier), and 25% aa (affected). Each pregnancy is an independent event with the same probabilities.