What condition typically indicates that a trait is passed down through X linked recessive inheritance?

• A. Affected fathers passing traits to all daughters
• B. Affected individuals having at least one affected parent
• C. Affected individuals predominantly being males
• D. Affected individuals having affected parents

Answer: (C)

In X-linked recessive inheritance, a key characteristic is that affected individuals are predominantly male. This is because males have only one X chromosome (XY), so if they inherit a recessive allele on that X chromosome, they will express the trait. In contrast, females have two X chromosomes (XX), meaning they can be carriers of the trait if they have one affected X chromosome but may not express the trait unless they inherit affected alleles on both of their X chromosomes.

Due to this pattern of inheritance, most of the affected individuals in a family tree are typically males. This pattern contrasts with autosomal traits, where traits can be passed to both males and females with equal likelihood. Thus, observing a high prevalence of affected males within a family or population is a strong indicator of X-linked recessive inheritance.