How is hemophilia inherited?

Hemophilia is an X-linked recessive genetic disorder. This means that the gene responsible for the disorder is located on the X chromosome. Males are more likely to have hemophilia than females because males only have one X chromosome, while females have two.

If a male has one copy of the hemophilia gene, he will have the disorder. If a female has one copy of the hemophilia gene, she will be a carrier. Carriers do not have the disorder themselves, but they can pass the gene on to their children.

The inheritance pattern of hemophilia can be illustrated using a Punnett square. A Punnett square is a diagram that shows all possible combinations of genotypes for two parents.

In the case of hemophilia, the Punnett square would look like this:

```

| | Xh Y|

--+----------------+

| XH| XH Xh XH Y

| Xh| Xh Xh Xh Y

```

- XH represents the normal allele for the clotting factor VIII gene.

- Xh represents the hemophilia allele for the clotting factor VIII gene.

- Y represents the male sex chromosome.

The Punnett square shows that there are four possible genotypes for the offspring of a male with hemophilia and a female who is a carrier.

- The chances of having a son with hemophilia are 50%.

- The chances of having an unaffected son are 50%.

- There is a 25% chance of having a daughter with hemophilia.

- There is also a 25% chance of having a daughter who is a carrier of hemophilia.

Hemophilia can also be inherited in a rare autosomal dominant form, in which case both males and females can be affected.