A genetic disorder is defined as a disease that is caused by an abnormality in an individual’s DNA. Genetic disorders can be sex-linked, mutations of genes, or caused by heredity. One genetic disorder that is sex-linked and recessive is Hemophilia. Hemophilia is a rare, potentially dangerous bleeding disorder that slows the blood clotting process greatly. The following are a few pieces of information about this particular genetic disorder. Hemophilia was officially named and discovered in 1803 by Dr. John Conrad Otto, a physician from Philadelphia, though it most likely existed for many years prior. The first written account of a "disease" named Albucasis, which was actually the first case of Hemophilia, dates back to the 2nd Century in Babylonian Talmud. The description was written by Rabbi Judah haNasi, about a woman who died after having her third child from prolonged bleeding. Hemophilia has also been studied by other scientists, such as Barbara McClintock, who first recognized jumping DNA in studies of odd inheritance patterns that could lead to excessive bleeding. Hemophilia is a sex-linked (x-linked), recessive disorder. Genes for blood clotting are located on the X chromosome. Hemophilia is inherited when one of the X chromosomes is defective. In this kind of inheritance, people may be carriers of the trait for Hemophilia. This means that they may possess the genotype for the disorder but do not show signs of it. This also leads to why Hemophilia has been observed to follow a criss-cross pattern of inheritance, meaning that this disorder is predominantly found in males because females have a lower probability of inheriting 2 defective X chromosomes. There is one clear symptom of Hemophilia, which is excessive bleeding after any physical injury. Those who suffer from the disorder may bleed for weeks with just a small cut. In the most severe and rare cases, the bleeding may never actually stop. Frequent nose bleeds are another sign that could mean Hemophilia. There is only one treatment that can be used to effectively stop Hemophilia. This treatment is called Replacement Treatment, during which the clotting factor which is not present on the defective X chromosome is periodically provided for patitents using blood transfusions.