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. Author manuscript; available in PMC: 2009 Jul 13.
Published in final edited form as: Hum Hered. 2007 Oct 12;65(3):154–165. doi: 10.1159/000109732

Table A1.

Joint genotype probabilities for two siblings

X1 X2 P(X1, X2)
AA AA 0.25 p2 (1 + p)2
AA Aa 0.5 p2 (1 − p2)
AA aa 0.25 p2 (1 − p)2
Aa AA 0.5 p2 (1 − p2)
Aa Aa p(1 − p)(1 + p(1 − p))
Aa aa p(1 − p)2(1 − 0.5 p)
aa AA 0.25 p2 (1 − p)2
aa Aa p(1 − p)2(1 − 0.5 p)
aa aa (1 − p)2(1 − 0.5 p)2

p is the population frequency of disease susceptibility allele A.