The "royal gene" most often refers to the gene for hemophilia, particularly as it affected several European royal families.
Hemophilia is a genetic disorder that impairs the body's ability to make blood clots, a process needed to stop bleeding. This can result in prolonged bleeding after injury, surgery, or even spontaneously. The form of hemophilia primarily associated with the European royal families is hemophilia B, also known as Christmas disease. It's caused by a mutation in the F9 gene, which provides instructions for making clotting factor IX.
How it Spread Through Royalty
Queen Victoria of the United Kingdom was a carrier of the hemophilia gene. She herself was unaffected, but she passed it on to several of her children. Through their marriages into other royal houses, the gene spread to the royal families of Spain, Russia, and Germany.
Here's a simplified illustration:
| Carrier | Married Into | Offspring Affected |
|---|---|---|
| Queen Victoria | Various | Alice (carrier), Beatrice (carrier), Leopold (affected) |
- Alice: Alice's daughter, Alexandra, married Tsar Nicholas II of Russia. Their son, Alexei, suffered from hemophilia.
- Beatrice: Beatrice also passed the gene on, leading to cases in the Spanish royal family.
- Leopold: Leopold, one of Queen Victoria's sons, was affected by hemophilia, showing the direct inheritance of the condition.
Important Considerations
- Not a "royal" gene in origin: The term "royal gene" is a misnomer. The mutation causing hemophilia can arise in any family, not just those of royal lineage. It just so happened that it was present in Queen Victoria, which led to its propagation through various royal families due to the nature of royal intermarriage.
- X-linked inheritance: Hemophilia B is an X-linked recessive disorder. This means the gene is located on the X chromosome. Males (XY) only need to inherit one copy of the mutated gene to be affected, while females (XX) need to inherit two copies (one from each parent) to be affected. If a female has only one copy, she is a carrier and typically doesn't show symptoms but can pass the gene to her children.
- Modern Genetics: Modern genetic testing can identify carriers and affected individuals, allowing families to make informed decisions regarding family planning.
