Illustration of the 21 bp insertion/deletion polymorphism (SLC6A1 long and short alleles) and the insertion/deletion GG allele in the SLC6A1 gene. Picture (A) shows position of -24794 A/G SNP, 21 bp insertion and GG deletion. Picture (B) shows the sequence for the SLC6A1 short and long alleles and the -24794 A/G SNP. The A allele of the -24794 always coincided with the long allele in our populations. Sequence for the GG insertion/deletion polymorphism is presented in picture (C).