format
A data frame with 23 observations on 1305 variables. The columns are ID, FID MID, SEX, AFF, M1_1, M1_2, ..., M650_1, M650_2. The first 5 columns describe the pedigree structure and affection status, while the final 1300 columns contain the marker alleles. All markers are SNPs, whose alleles are written as 1 and 2. Missing alleles are denoted by 0.