Question

Why is it not surprising that the incidence of X-linked cognitive disorders is usually much higher in males compared to females?

Answer 1

X - linked cognitive disorders happen due to X linked recessive inheritance.

A mutation in a X - chromosome gene causes the phenotype to be expressed in males . This happens because of 2 reasons.

Females inherit 2 X chromosomes therefore They have twice the chance of getting a normal allele. Inheriting one X chromosome without mutation compensates for the other X chromosome which may have a mutation. Such females become carriers for the mutation and may pass it to their offsprings.

Men inherit only one X chromosome and thus have more chances of inheriting the gene with mutation.

So for a female to be effected, she has to receive the genes with mutation from both parents , while a male has to inherit the gene from mother only, chances of which are higher.