Thursday, February 19, 2009

What are the possible genotypes of the parents?

Since the disease is X-linked, it is recessive.
  1. If the mother is a carrier (XB Xb) and the father is healthy (XB Y), then there is a 25% chance that they will have a boy who is healthy (XB Y). There is also a 25% chance that there will be a girl who is completely healthy (XB XB). There is also a 25% chance that there will be a girl who is a carrier (XB Xb) and a 25% chance that there will be a boy that completely has the disorder (Xb Y).
  2. If the father has the disorder (Xb Y) and the mother is a carrier (XB Xb), then there is a 25% chance that there will be a girl who is a carrier (XB Xb) and a 25% chance that there will be a girl that completely has the disorder (Xb Xb). There is also a 25% chance that there will be a boy who is completely healthy (XB Y), and a 25% chance that the there will be a boy who completely has the disorder (Xb Y).
  3. If the father completely has the disorder (Xb Y) and the mother is healthy (XB XB), then there is a 50% chance that there will be a girl who is a carrier (XB Xb), and a 50% chance that there will be a boy who is completely healthy (XB Y).
  4. If the father is completely healthy (XB Y), and the mother completely has the the disorder (Xb Xb) then there is a 50% chance that they will have a girl that is a carrier (XB Xb), and a 50% chance that they will have a boy that completely has the disorder (Xb Y).
  5. If the father completely has the disorder (Xb Y), and the mother completely has the disorder (Xb Xb) then there is a 50% chance that they will have a girl that completely has the disorder (Xb Xb), and there is a 50% chance that they will have a boy who completely has the disorder (Xb Y).

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