Hemophilia Essay

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Hemophilia is the oldest known hereditary bleeding disorder. There are two types of hemophilia, A and B (Christmas Disease). Low levels or complete absence of a blood protein essential for clotting causes both. Patients with hemophilia A lack the blood clotting protein, factor VIII, and those with hemophilia B lack factor IX. A person with severe hemophilia has less than 1% of the normal amount of a clotting factor - either Factor VIII (8) or Factor IX (9). People without hemophilia have between 50-150% of the normal level of factor VIII or IX. There are about 20,000 hemophilia patients in the United States. Each year, about 400 babies are born with this disorder. Approximately 85% have hemophilia A and the remainder has hemophilia B.…show more content…
Because the genetic defect occurs on the X chromosome, women are carriers of hemophilia but rarely have the disorder. Hemophilia occurs almost exclusively in men.
In about one-third of the babies born with hemophilia, the disorder is believed to be due to a spontaneous mutation of the gene. There is no family history of hemophilia. To determine a sex linkage inheritance of a defective trait, look at a family pedigree to notice the similarities and patterns of the trait throughout the family pedigree for example the pedigree below:

Normal Female Normal Male

Normal, but known carrier female Affected Male

The first generations are skipped, although Nicolas (1904-18) was a hemophiliac, neither his parents nor grandparents were. This pattern occurs in several other places of the pedigree, and indicates a recessive mode of inheritance. From the biochemical nature of the defect, scientists have determined that hemophilia is a recessive trait. All the affected individuals are sons, strongly suggesting that the defect is a sex linkage trait. Since males are hemizygous for the X chromosome, more males than females should have the phenotype of

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