7. The hereditary nature of hemophilia, an X-linked recessive disorder, was first described in the medical literature by the Arab physician Abulcasis, in the 10th century AD. Nonetheless, some understanding of certain concepts of hemophilia transmission is already evident in much earlier writings. As early as in the 2nd century AD, the Talmud (compendium of Jewish civil law) decreed that if a woman had two sons who both died at circumcision, the third son must not be circumcised. Furthermore, if two sisters had their sons circumcised and the sons of both mothers died of bleeding, the third sister should not have her son circumcised. The Talmud, however, does not exempt the sisters' brother's son from circumcision. What is the probability that a woman's third son will die of hemophilia if two older sons of hers died bleeding at circumcision? What is the probability that if two sisters' sons died, the third sister's son will also die of bleeding? If two sisters' sons died of bleeding, why is the son of their brother not exempt from circumcision? Is this an inadvertent omission from the Talmud, or does it make biological sense?
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If a woman has two sons who both died of hemophilia, it means that she is a carrier of the hemophilia gene (XhX). The father of the children must have a normal X chromosome (X) and a Y chromosome (Y) since he does not have hemophilia. So, the mother's genotype is Show more…
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Adi S.
Another type of blood disorder is hemophilia, which is a linked disorder caused by a recessive allele. Like VWD, this disorder interferes with the protein involved in blood clotting. It is known as "bleeder's disease" because even minor injuries can become life-threatening. This disorder is considered more severe than VWD. In both cases, there are versions of the disorder that can be less or more severe, depending on which protein or clotting factor is affected. Xhxm Normal Xhy Normal Xhxh Carrier xhy Hemophilia Xhxh Hemophilia If a woman is a carrier, what percentage of her SONS will have the disorder? How many (%) of their sons will have hemophilia? How many (%) of their sons will be normal? How many (%) of their daughters will be normal? A man who has hemophilia marries a normal woman (not a carrier). How many (%) of their sons will have hemophilia? How many (%) of their daughters will be carriers? A woman who is a carrier marries a man with hemophilia. How many (%) of their sons will have hemophilia? How many (%) of their daughters will be carriers?
Sri K.
Title: Human Pedigrees, Meiosis, and Probability: Hemophilia Hemophilia is a genetic disorder in which the enzymes required for blood clotting do not function properly, leading to prolonged periods of bleeding after even minor cuts. Hemophilia can be caused by mutations in several proteins, including two encoded by genes on the X chromosome: factor VIII (the XF8 locus) and factor IX (the XF9 locus). Recessive mutations in either of these genes cause hemophilia. These loci are far enough apart on the X chromosome (see figure) that they show independent assortment. The pedigree below shows a family in which some members have hemophilia caused by mutations in XF8 or XF9. Assume that individual |-1 does not carry any recessive alleles for these loci. Chr X: female male Shaded: hemophilia Factor VIII mutation Factor IX mutation Indicate dominant alleles: XF, XFQ Indicate recessive alleles: Xto, Xt9 a) Draw a diagram of the metaphase of a non-aberrant (normal) meiosis in individual III-2 that could produce a gamete that would carry both the Xf8 and the Xf9 hemophilia alleles. You need only show the sex chromosomes as they are lined up at the metaphase plate; ignore the autosomes. [3 pts] Metaphase in [II-2]: spindle pole b) Individuals III-1 and III-2 are planning to have a third child, IV-3. Calculate the probability that this child will have hemophilia. Explain each component of your calculations. (Ignore inactivation for this question) You may write your answer to the right-hand side of the meiosis cell. [3 pts]
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