Genotype indicator variable x is 1 for a particular genotype of interest, and 0 for other genotypes. For example, x=1,0,0 for AA, AB, BB is the indicator variable for the homozygous genotype AA. Using the same ITO matrices, the joint probability for AA-indicator variable x between two relatives is E[xrel1,xrel2]=P(xrel1=1,xrel2=1)=∑k=02P(xrel2=1|1,k)πkP(xrel1=1)=p2(π2+π1p+π0p2) and correlation coefficient is: (8)rAA−indicator=p2(π2+π1p+π0p2)−(p2)2p2(1−p2)=π2+π1p+(π0−1)p21−p2 Similarly, for AB and BB indicator variable, (9)rAB−indicator=π2+π1/2+(π0−1)2pq1−2pqrBB−indicator=π2+π1q+(π0−1)q21−q2
