Why are sex-linked traits more common in males than in females?

Question

Recessive alleles on the X chromosome will always produce the trait in a male.

All alleles on the Y chromosome are recessive.

All alleles on the X chromosome are dominant.

Any allele on the Y chromosome will be codominant.

Answer 1

Sex-linked traits are more common in males because males only have one X chromosome, while females have two. This means that if a male inherits a recessive allele for a sex-linked trait on his X chromosome, he will exhibit that trait because he does not have another X chromosome with a dominant allele to mask it. In contrast, females would need to inherit two copies of the recessive allele (one from each parent) in order to exhibit the trait, making it less common in females. Additionally, the Y chromosome does not carry as many genes as the X chromosome, so there are fewer opportunities for sex-linked traits to be expressed in males.