Several studies have reported either higher levels of testosterone among rapists or the correlation of shorter CAG repeats with criminal activities. However, to date, no study has analyzed AR gene in rapists worldwide.
February 24, 2009
By Syed Akbar
Hyderabad, Feb 23: Criminal activity has genetic basis too. Though
most of the crimes recorded in the world are influenced by
environmental factors, genes too play a crucial role in pushing people
to commit crimes.
Scientists at the city-based Centre for Cellular and Molecular Biology
have found that the androgen receptors (AR) gene containing Cytosine,
Adenosine and Guanine (CAG) repeat, plays an important role in
shaping the criminal mentality or otherwise of an individual. Those
with shorter repeat of CAG in their AR gene develop antisocial
personality disorders. On an average the CAG repeats 21 times in
normal people and 18 or less number of times in those with criminal
bent of mind.
In the first-ever study conducted on criminals from Indian
subcontinent, the CCMB team analysed the AR-CAG repeat length in
645 men, of which 241 were convicted for rape, 107 for murder, 26 for
both murder and rape, and 271 were control males.
"We found significantly shorter CAG repeats in the rapists (18.44
repeats) and murderers (17.59 repeats) compared to the control men
(21.19 repeats). The criminals who committed murder after rape had a
far shorter mean repeat length (17.31 repeats) in comparison to the
controls or those convicted of rape or murder alone. Our study
suggests that the reduced CAG repeats in the AR gene are associated
with criminal behaviour. This, along with other studies, would help in
understanding the biological factors associated with the antisocial or
criminal activities," CCMB senior scientist Dr K Thangaraj told this
AR gene has strong effect on the function of the central as well as
peripheral nervous system and plays a crucial role in maintaining
masculine reproductive behaviour. Shorter CAG repeats are related to
personality scales characterised by dominance, high verbal aggression,
high monotony avoidance, and low lack of assertiveness in
"Antisocial activities like aggression and tendency to rape or murder,
once thought to be personality specific and influenced by environment
rather than by genes, are gaining more attention among geneticists. Our
present study on AR-CAG repeat length in individuals convicted for
rape or murder revealed a significant difference in the mean length and
distribution of the AR alleles between criminals and the control men.
The association of increased androgens levels or the shorter CAG
repeat length with antisocial activities may indicate additional factors
associated with the criminal activities," Dr Thangaraj said.
A genetic study on criminals may help in understanding if there is some
biological factor, which may affect psychological state of an individual,
and also in proper management and reducing the social burden due to
these offences, if the biological basis of such offenses is established, he