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Showing Revision 1 created 09/29/2013 by Cogi-Admin.

  1. If we only were to focus on two
  2. generations let's say for a dominant and recessive
  3. trait in a pedigree, we could really be
  4. missing information. Take this example here. I have
  5. two very small pedigrees of just an immediate
  6. family and they show the same affected inheritance
  7. pattern where one child, one daughter is affected.
  8. But one of these pedigrees is for a recessive
  9. trait that both parents have an allele for, but
  10. they're unaffected and then they pass both of those
  11. recessive alleles on to the daughter. And the other
  12. pedigree is from a very new spontaneous mutation that's
  13. causing a dominant trait but the question is, can
  14. you tell the difference? I can't. The only way
  15. to distinguish these two possibilities would be to zoom
  16. out on both pedigrees and fill out as much family
  17. information as we can. This family history is going to
  18. be able to help us figure out which one
  19. of these is a recessive trait pedigree and which
  20. one of these is a spontaneous mutation that's caused a
  21. new dominant trait. For example this pedigree on the
  22. right is most likely the pedigree of a recessive trait.
  23. Because we now see that there's a family history.
  24. Unaffected parents with affected offspring, the traits skip generations and
  25. we see it on both sides of the
  26. family. Whereas the other pedigree is mostly likely caused
  27. from our spontaneous mutation and the new dominant trait
  28. because we don't have any family history of it,
  29. whatsoever. Although again, this could still possibly be a
  30. result of limited information. And maybe we just need
  31. to zoom out even further to tell if it's
  32. actually another possibility of it being a recessive pedigree
  33. as well. The point is, is that any time we're really doing this in real life.
  34. We try to get as much information as
  35. possible and specifically when we're trying to distinguish
  36. these two scenarios, what we're looking for is a family history
  37. of the condition. Meaning that you've got maybe more than one affected
  38. sibling or parent or close relative, or even possibilities of
  39. [UNKNOWN]
  40. relationships. Effectively reproduction with close relatives.