Question

Determine whether the following scenarios are sex-linked, sex-limited or sex-influenced: "A woman with congenital generalized hypertrichosis, an X-linked dominant disorder, has only patchy hairiness, while her brother with the same condition is covered to toe with hair.

Answer 1

The condition described, congenital generalized hypertrichosis, is an X-linked dominant disorder. Males show full expressivity while females may have a milder form due to X-inactivation, which exemplifies sex-linked inheritance patterns.

Step-by-step explanation

In the scenario described, the congenital generalized hypertrichosis, which appears as X-linked dominant, results in complete hairiness in a male, while a female with the same condition has only patchy hairiness. This discrepancy is directly related to the nature of sex-linked inheritance of traits on the X chromosome. In sex-linked disorders, males express the phenotype with just one copy of the mutant allele since they have only one X chromosome. Females, with two X chromosomes, may present a milder form of the trait due to X-inactivation, which provides a form of dosage compensation for the difference in X chromosome number between the sexes.

Therefore, the given condition is an example of a sex-linked (specifically, X-linked) disorder, rather than sex-limited or sex-influenced. In this scenario, X-linked dominant inheritance is evidenced by the affected status of both the male and the female siblings, though the trait's expressivity differs between them, which is common in such disorders.