These samples were made available by the Framingham SHARe resource, which contains genotypes for all respondents using the Affymetrix 5.0 genotyping platform. After we reduced the Framingham SHARe data set to trios with complete (nonmissing) genetic information (i.e., genotypes for biological mother, biological father, and focal subject), our analytic sample included 1,877 trios. Because we are interested in interaction terms, we eliminated SNPs that have fairly low minor allele frequencies (those with MAF <5 %). If the minor allele frequency is .05, we would expect roughly one-quarter of 1 % (.052) of people in the sample to be homozygous for the minor allele; in a study of our size, that translates to roughly five people. We also dropped SNPs that did not meet the Hardy Weinberg equilibrium (HWE) criterion. If the minor allele frequency is p and the alternate allele frequency is q, then the HWE is a simple one-degree-of-freedom chi-square test of independence in which the observed genotype frequencies are compared with the expected frequencies given the frequencies for each allele, where the expected frequencies are given as p2,
