gender: 1 - male; 2 - female
r' in the group names corresponds to the grouping factor, e.g.: DRD2_A_rT has two values: 1 if the genotype contains the T allele, 0 if not
in case of VNTRs 'r' numbers mean the presence (value 1) or the absence (value 0) of the particular allele 
empty cells corresponds to missing values
123 categories correspond to the quantification of the genotype groups: 1 -  homozygote group 1; 2 - heterozygotes; 3 - homozygote group 2 (in alphabetical or numerical order)