examining RNA transcript levels and genotype data for individuals in the top two generations of the Centre d'Etude du Polymorphism Humain (CEPH) pedigrees (21). The CEPH pedigrees are three generation pedigrees with a structure similar to that of the cartoon pedigree in Figure 1. The top two generations of several of these pedigrees were genotyped at more than 830,000 genetic markers in the first phase of the International HapMap Project (103). Using genotypes for approximately 6,500 genetic markers genotyped by the SNP consortium in all three generations of the pedigrees (85), Burdick and colleagues proceeded to impute genotypes for most of these markers in the third generation of these pedigrees (12). They showed that this imputation based analysis was more powerful than the original analysis which examined only directly genotyped markers for each individual.
