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Hemophilia figured prominently in the history of European royalty in the 19th and 20th centuries. Britain's Queen Victoria, through two of her five daughters (Princess Alice and Princess Beatrice), passed the mutation to various royal houses across the continent, including the royal families of Spain, Germany and Russia. Victoria's son Prince Leopold, Duke of Albany suffered from the disease. For this reason, haemophilia was once popularly called "the royal disease". Tests of the remains of the Romanov imperial family show that the specific form of haemophilia passed down by Queen Victoria was probably the relatively rare Haemophilia B.〔("Case Closed: Famous Royals Suffered from Hemophilia". ) Michael Price, ScienceNOW, October 9, 2009.〕 The sex-linked X chromosome disorder manifests almost entirely in males, although the gene for the disorder is located on the X chromosome and may be inherited from either mother or father. Expression of the disorder is much more common in males than in females. This is because, although the trait is recessive, males only inherit one X chromosome, from their mothers. Thus if the haemophilia gene is transmitted on it, there is no possibility for the male to inherit a haemophilia-free gene from his father to mask or dilute the symptoms. By contrast, a female who inherits a gene for haemophilia on one of her X chromosomes will also have inherited a second X chromosome from the other parent which is likely to carry a haemophilia-free gene that would prevent full expression of symptoms. Females who inherit the gene for Haemophilia A or B from both parents would be expected to manifest full symptoms, similar to those seen in affected males, but this is extremely rare. Despite frequent inter-marriage among royalty, no case of such double inheritance is known among Queen Victoria's descendants. Although an individual's haemophilia can usually be traced in the ancestry, in about 30% of cases there is no family history of the disorder and the condition is speculated to be the result of spontaneous mutation in an ancestor. Victoria appears to have been a spontaneous or ''de novo'' mutation and is usually considered the source of the disease in modern cases of haemophilia among royalty. Queen Victoria's father, Prince Edward, Duke of Kent, was not a haemophiliac, and the probability of her mother having had a lover who suffered from haemophilia is minuscule given the low life expectancy of 19th-century haemophiliacs. Her mother, Victoria, Duchess of Kent, was not known to have a family history of the disease, although it is possible that the mutation began at her conception and was passed down only to Victoria and not to her other children. In the same way, had Queen Victoria herself only had seven children, the mutation would probably be assumed today to have occurred at the conception of Princess Alice, as she was the only known carrier among Victoria and Albert's first seven children. Queen Victoria's eldest daughter, Victoria, Princess Royal, apparently escaped the haemophilia gene as it did not appear in any of her matrilineal descendants. Victoria's fifth child, Helena, may or may not have been a carrier; two healthy sons survived to adulthood but two other sons died in infancy and her two daughters did not have issue. Victoria's sixth child, Louise, died without issue. Her sons King Edward VII, Alfred, and Arthur were not haemophiliacs. However, her daughters Alice and Beatrice were confirmed carriers of the gene, and her son Leopold was a sufferer of haemophilia, making his daughter Princess Alice, Countess of Athlone a carrier as well. == Queen Victoria family tree== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「haemophilia in european royalty」の詳細全文を読む スポンサード リンク
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