The identity of the "cursed blood" disorder that troubled the British Royal Family in the 19th and early 20th centuries has been revealed.
DNA analysis show that the disease inherited by Queen Victoria's descendants was probably a severe form of the blood clotting disorder haemophilia B, according to the study published in journal Science.
To reach the conclusion, scientists examined DNA samples extracted from the skeletal remains of Russia's Romanov family and also of Queen Victoria's great grandson Crown Prince Alexei, reports The BBC.
Through analyses, they discovered a mutation in a gene on the X chromosome that codes for the production of Factor IX, a substance that causes blood to clot. This genetic mutation is the cause of haemophilia B.
Since this blood disorder is linked to the X chromosome it passed on through the maternal line, but is only manifested in male descendants.
This is because males have only one X chromosome, so the mutation on that single chromosome is "expressed" as the disease. Females only carry the disease, because their second X chromosome is extremely unlikely to have this same, very rare mutation.
Lead researcher Dr Evgeny Rogaev from the University of Massachusetts told the BBC that it was the "final chapter" in the confirmation of the Romanov family's remains.
He added: "We have resolved a medical mystery from the past."