Hemophilia: Why is it More Common in Males?

Hemophilia is a genetic disorder caused by a deficiency in blood-clotting factors. The genes that code for these factors are located on the X chromosome, one of the two sex chromosomes. Males have only one X chromosome, while females have two.

If a male inherits a defective copy of the gene that codes for a blood-clotting factor, he will have hemophilia. If a female inherits one defective copy of the gene, she will be a carrier of hemophilia, but she will not have the disorder herself.

This is because the normal copy of the gene on her other X chromosome will compensate for the defective one. However, if a female inherits two defective copies of the gene, she will have hemophilia.

Therefore, males are more likely to be afflicted with hemophilia than females because they have only one X chromosome and therefore cannot rely on a second normal copy of the gene to compensate for a defective one.