Question

Explain why X-linked recessive traits are more common in males than females.

Hint: If you are stuck, try explaining why a boy (XbY) has colour vision deficiency and a girl (XBXb) does not, even though they both have the recessive allele Xb.

Answer 1

X-linked recessive traits are more common in males than females because males only have one X chromosome while females have two. This means that if a male inherits an X chromosome with a recessive allele, it will be expressed in his phenotype.

Answer 2

X-linked recessive traits are more common in males because the decease is only carried on the X chromosome therefore females need two copies of the gene to have the decease whereas in males they only need one copy. This is because males are XY and females are XX