The polymorphism of dopamine receptor D4 (DRD4) and dopamine transporter (DAT) genes in the men with antisocial behaviour and mixed martial arts fighters.

Variable-number tandem repeat (VNTR) polymorphisms of DRD4 and DAT genes were studied in the Russian and Chechen men convicted of crimes, and two control groups comprised of the MMA fighters and a sample of general population. A group of MMA fighters included only the subjects without history of antisocial behaviour. DNA was isolated by phenol-chloroform extraction from the blood.