Question

Under what condition does a female express haemophilia?

Options

• When she inherits the allele from her mother only

• When she has the genotype XᴴY

• When both X chromosomes carry the recessive gene (XʰXʰ)

• When she is a carrier (XᴴXʰ)

Answer 1

A female expresses haemophilia only when both X chromosomes carry the recessive haemophilia gene, resulting in the genotype XʰXʰ. This is rare because it requires both her mother and father to carry or express the haemophilia allele. With only one recessive allele (XᴴXʰ), she is a carrier but does not suffer from haemophilia.