An alternative method of genotyping large cohorts is to analyze pools consisting of multiple DNA samples (reviewed in (Sham et al., 2002)), which was developed to reduce genotyping costs. Analysis of pooled samples still allows a comparison of allele frequencies between cases and controls. Pools are made from cases or control subjects, either as one pool containing the case samples and the other containing the controls, or as multiple pools of each category of subjects. This technique has been used successfully to find differences in allele frequencies using microarrays (Kirov et al., 2006, Liu et al., 2006, Liu et al., 2005, Johnson et al., 2006, Uhl et al., 2007, Uhl et al., 2008).
