How Hemophilia Is Inherited
Hemophilia is a rare disorder where the person is unable to stop bleeding due to a lack of certain blood clotting factors. It’s a genetic disease that’s passed down through the X chromosome. Almost all people with hemophilia are male, however, women can be carriers of the disease.
The likelihood of being born with hemophilia depends on certain factors. Males are born with one X chromosome and one Y chromosome, whereas females are born with two X chromosomes. The disease is passed down if there is a fault on the X chromosome and there are three different inheritance patterns.
If the mother is a carrier:
If the mother is a carrier it’s likely that she may pass down one copy of the X chromosome. There is a 50 percent chance that she’ll pass down the mutated chromosome to her daughters who will become carriers and a 50 percent chance that she’ll pass down the gene to her sons who will develop the disease.
If the father has hemophilia:
Male sperm will either contain an X chromosome or a Y chromosome. Fertilized eggs from X chromosomes will become female and fertilized eggs from Y chromosomes will become male. This means that none of his sons will develop hemophilia because they will inherit their mother’s healthy X chromosome, but his daughters will have a 50-50 chance of becoming carriers of the disease.
If both the mother is a carrier and the father has hemophilia:
In the extremely rare event that both the mother and father have the affected X chromosomes then there is a 50 percent chance that their sons will be born with hemophilia. There will be a 50 percent chance that their daughters will be carriers and a 50 percent chance they will also have the condition.
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