Consider a trait determined by a rare, simple Mendelian, autosomal recessive allele. What is the concordance between identical twins? Between same-sex fraternal twins?
A)identical concordance = 1; fraternal concordance = 0.071
B)identical concordance = 1; fraternal concordance = 0.143
C)identical concordance = 1; fraternal concordance = 0.250
D)identical concordance = 1; fraternal concordance = 0.333
E)identical concordance = 1; fraternal concordance = 0.500

Question

Quizplus · Accepted Answer

Identical twins share 100% of their genes, so the concordance for a recessive trait is 1. Fraternal twins share 50% of their genes, so the probability both have the recessive allele is 0.5 * 0.5 = 0.25, and since it's a rare trait, the concordance is approximately 0.143.

Consider a Trait Determined by a Rare, Simple Mendelian, Autosomal