Genes and violent criminals

Three genes may play a strong role in determining why some young men raised in rough neighborhoods or deprived families become violent criminals, while others do not. One gene called MAOA that played an especially strong role has been shown in other studies to affect antisocial behavior - and it was disturbingly common, the team at the University of North Carolina reported. People with a particular variation of the MAOA gene called 2R were very prone to criminal and delinquent behavior, said sociology professor Guang Guo, who led the study. "I don't want to say it is a crime gene, but 1 percent of people have it and scored very high in violence and delinquency," Guo said. His team, which studied only boys, used data from the National Longitudinal Study of Adolescent Health, a U.S. nationally representative sample of about 20,000 adolescents in grades 7 to 12. They found specific variations in three genes -- the monoamine oxidase A (MAOA) gene, the dopamine transporter 1 (DAT1) gene and the dopamine D2 receptor (DRD2) gene -- were associated with bad behavior, but only when the boys suffered some other stress, such as family issues, low popularity and failing school. MAOA regulates several message-carrying chemicals called neurotransmitters that are important in aggression, emotion and cognition such as serotonin, dopamine and norepinephrine.