Why are X-linked disorders more common in males?

Why are X-linked disorders more common in males?

• A. Males have two X chromosomes
• B. Males have only one X chromosome; a single recessive allele on X will be expressed since there is no second X to mask it
• C. Y chromosome carries the recessive allele
• D. Males have higher mutation rates on autosomes

Answer: (B)

In X-linked recessive traits, males are more often affected because they have only one X chromosome. That means any recessive allele on their single X is expressed, since there isn’t a second X to mask it with a normal copy. Females have two X chromosomes, so a recessive allele on one X can be masked by a normal allele on the other X, making them typically carriers rather than affected. The Y chromosome doesn’t provide a matching copy of the X-linked gene, so it can’t hide the recessive allele. This is why a single recessive allele on the X will show up in males even if the same allele would be hidden in females.

In X-linked recessive traits, males are more often affected because they have only one X chromosome. That means any recessive allele on their single X is expressed, since there isn’t a second X to mask it with a normal copy. Females have two X chromosomes, so a recessive allele on one X can be masked by a normal allele on the other X, making them typically carriers rather than affected. The Y chromosome doesn’t provide a matching copy of the X-linked gene, so it can’t hide the recessive allele. This is why a single recessive allele on the X will show up in males even if the same allele would be hidden in females.