Match each statement (a–e) with the best answer from the following list: consultand, 50%, prior probability, 66.7%, obligate carrier, 100%.

The probability that the healthy brother of a woman with an autosomal recessive condition is a heterozygous carrier

Key Concepts

Autosomal Recessive Inheritance

Autosomal recessive inheritance occurs when a trait or condition is expressed only when an individual has two copies of a recessive allele. In this case, both parents must carry at least one recessive allele for their offspring to potentially inherit the condition. If a woman has an autosomal recessive condition, it indicates that she has two recessive alleles, while her healthy brother may carry one or none.

Carrier Probability

A carrier is an individual who possesses one copy of a recessive allele for a genetic condition but does not exhibit symptoms. In the context of autosomal recessive conditions, the probability that a sibling of an affected individual is a carrier can be calculated based on the parents' genotypes. If the affected individual has two recessive alleles, the probability that a healthy sibling is a carrier is influenced by the parents' carrier status.

Prior Probability

Prior probability refers to the initial estimation of the likelihood of an event before new evidence is considered. In genetics, this concept is crucial for determining the probability of a sibling being a carrier based on known information about the family. For example, if both parents are carriers of an autosomal recessive condition, the prior probability of their healthy son being a carrier is 66.7%, as he has a 2 in 3 chance of inheriting one recessive allele.