What is the approximate risk for the wife of a man whose family history includes cystinosis, an autosomal recessive disorder?

• A. 1/2
• B. 2/3
• C. 1/50
• D. 1/100

Answer: (D)

In understanding the risk for the wife of a man with a family history of cystinosis, it's essential to recognize that cystinosis is an autosomal recessive disorder. This means that a child must inherit two copies of the mutated gene (one from each parent) to express the disorder.

If the man has a family history of cystinosis, it suggests that he may be a carrier of the cystinosis gene mutation, even if he does not exhibit symptoms of the disease himself. The chance that he is a carrier depends on his family lineage and the presence of cystinosis among family members. However, without specific information indicating that he is a carrier (e.g., if he has affected relatives), a general assumption is made that he has a 1 in 2 chance of being a carrier (because he could inherit one normal and one mutated allele).

For the wife, if we assume that she is unaffected and there is no other known family history of cystinosis in her lineage, she would have only a small chance of being a carrier, likely less than the frequency of the disorder in the general population.

Thus, when calculating the overall risk of their offspring being affected by cystinosis, given that the wife's carrier status