Which statement describes X-linked inheritance?

• A. Female carriers, males affected (skips generations via carriers).
• B. Males and females equally affected.
• C. Requires mutations in both X chromosomes to manifest.
• D. Only autosomal genes involved.

Answer: (A)

X-linked inheritance involves genes located on the X chromosome. Because males have only one X, a single mutated allele on that X will typically cause the disease in a male. Females have two X chromosomes, so one mutated allele usually makes them carriers rather than affected. When a mother is a carrier, her sons have a good chance of being affected, while daughters often become carriers. This pattern can appear to skip generations because an affected male may appear in a later generation due to transmission through carrier females, even if the females themselves are not affected. Therefore, female carriers and affected males, with transmission through carriers, best describes X-linked inheritance. The other statements don’t fit this pattern: the trait isn’t usually equal in males and females, it doesn’t require two mutated Xs to manifest for typical X-linked patterns, and autosomes (not the X chromosome) would be involved for autosomal inheritance.