Question

Hemophilia is a gender-linked blood disorder in humans. The gene responsible for it is gene-linked recessive, meaning it is present on the X chromosome. When the gene is present in males (Xh), it always expresses itself, meaning that the male's blood won't clot properly. When present in females in a heterozygous condition (XhXH), the gene doesn’t express itself; but the female becomes a carrier, meaning that her offspring could have hemophilia.. When present in a homozygous recessive condition in females (XhXh), it expresses itself. One of every 10,000 persons is affected by this disease. What could be the allele frequency for this disease in the entire population?

Answer 1

Hemophilia's expressive gene is carried by the mother herself. For a female child, it is impossible to have Haemophilia as one allele is being carried by father and that allele does not cause disease. In the male offspring, chances of being diseased are 50:50, as the female gene in half of the gametes will be dominant and half will be recessive. Therefore, out of 5000 male offsprings, 2500 bear the chances of getting Haemophilia.
But in real life situation, 1 out of 10000 people is affected.