Why is hemophilia carried by males but expressed in males and rarely in males?

Hemophilia is a genetic disorder caused by mutations in the X chromosome, which is one of the two sex chromosomes. Males have one X and one Y chromosome (XY), so if they inherit the mutated X chromosome, they will express the condition because there is no second X chromosome to provide a normal copy of the gene. Females, on the other hand, have two X chromosomes (XX), so they can be carriers of the mutation without expressing the disorder if their second X chromosome has a normal gene. This is why hemophilia is primarily expressed in males, while females are often carriers.