Mendelian IBD sharing of full siblings
= Mendelian IBD sharing of full siblings
{c}
{title2=$J\sim\operatorname{Bin}(2,1/2)$}
In an <outbred pedigree>, the two <full siblings> receive the same paternal copy with probability $1/2$, and independently the same maternal copy with probability $1/2$. Thus the number $J$ of shared copies has a <binomial distribution> with probabilities $(1/4,1/2,1/4)$, and $E[J/2]=1/2$.
// Target: biology.bigb