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Old 09-19-2006, 06:43 PM   #18
zwyatt
Quote:
Originally Posted by Kat
My point is that the original question was what the difference between parent->offspring and sibling->sibling was. In this case, using the approximation of .5 for sibling relatedness is incorrect, because it doesn't show the difference. For MOST applications you can use .5 because it simplifies things. But in this case, you cannot. It is not useful to say that parent->offspring and sibling->sibling pairings are identical, because they are NOT identical. For parent->offspring comparisons, the percentage of genes related is ALWAYS .5. For sibling->sibling comparisons, the percentage of genes related is ALMOST NEVER EXACTLY .5, but more than likely something close to that number.

-Kat
Okay, now we're getting somewhere! Would you agree that any given full sib pair is just as likely to have r<.5 as they are likely to have r>.5? From that perspective, wouldn't it be inaccurate to say that a parent->offspring mating is necessarily "safer" than a full sib mating?