An estimation of the number of susceptibility loci for isolated cleft palate.

The existence of a major gene (or genes) that contributes significantly to the familial clustering of cleft lip with or without cleft palate (CL(P)) has been suggested by genetic epidemiology studies and supported by patient-control genotype association studies with a candidate gene. Here we present an analysis of the familial recurrence risk data for isolated cleft palate (CP) and show that an oligogenic model with six genes of equal effect fits the data best. The discrimination between alternative models is, however, poor and a major locus that explains half of the familial recurrence is plausible. The prospects for identification of susceptibility loci for CP are discussed.