Let G denote the minor allele count for a subject (0, 1, or 2) and D denote the disease outcome (1 affected and 0 unaffected). Define the genotype relative risk (GRR) [21] as P(D=1∣G=x)P(D=1∣G=0)=ψxforx=1,2. For a multiplicative model, ψ1 = ψ and ψ2 = ψ2 ; equivalently, the log GRR is linear in G with coefficient β log(ψ). We wish to test the hypothesis ψ=0, using both case–control and family-based data.
