Why are X-linked recessive conditions more often expressed in males?

X-linked recessive conditions are expressed more frequently in males because of the fundamental difference in their sex chromosomes compared to females.12

In humans, females possess two X chromosomes (XX), while males possess one X and one Y chromosome. Because the Y chromosome is much smaller and carries far fewer genes than the X chromosome, it lacks the corresponding alleles necessary to counteract or suppress recessive mutations found on the male's single X chromosome. Consequently, a male who inherits a recessive X-linked mutation is considered hemizygous for that trait and will manifest the condition.1234

In contrast, a female must typically inherit the recessive allele on both of her X chromosomes to fully display the trait. If she inherits the mutation on only one X chromosome, she is generally an unaffected carrier, as the dominant allele on her second X chromosome masks the effect of the recessive one.234