In X-linked diseases, who are most likely to be unaffected carriers?

In X-linked diseases, females are most likely to be unaffected carriers due to their genetic makeup. Females have two X chromosomes, which means that if one X chromosome carries a mutation that causes an X-linked disorder, the other X chromosome may have a normal copy of the gene. This can result in the female being a carrier of the disease without expressing any symptoms, as the presence of a normal gene can often compensate for the mutated one.

In contrast, males have only one X chromosome and one Y chromosome. If a male inherits an X chromosome with a mutation, he will express the disease because there is no second X chromosome to potentially carry a normal allele that would mitigate the effects of the mutation. Therefore, males cannot be carriers in the same way that females can; they either have the disorder or they do not, while females can carry the mutation without being affected themselves.

Understanding the inheritance patterns of X-linked diseases highlights the differences in carrier status between the genders, hence the reason why females are considered the most likely to be unaffected carriers.