The MAOA gene codes for the enzyme monoamine oxidase-A. It is located on the X chromosome and is primarily responsible for the degradation of amine neurotransmitters, such as dopamine, norepinephrine and serotonin. These neurotransmitters control mood, aggression and pleasure. What is even more interesting is that low expression of the MAOA gene has now been linked to violent tendencies.
A recent study reported that males with low expression levels of the MAOA gene were about twice as likely to have used a weapon or joined gangs than 'normal' boys. The research focused on males because the MAOA gene is carried on the X chromosome, hence males only have one copy. Thus, males who possess a variant of the MAOA gene do not have a second copy to counteract any errors.
Interestingly, some common inhibitors of MAOA include tobacco and drugs used to treat depression and Alzheimer's. This increases the importance of accurate and specific measurement and monitoring of MAOA gene expression in high-risk category individuals.
If the level of expression of the MAOA gene can be measured, then an estimation of the likelihood of an individual getting involved in violent activities can be made. Although it would not be possible to change a violent individual's DNA, it could be feasible to alter the level of gene expression using a suitable miRNA or transcription factor.