Dangerous DNA: The Warrior Gene

15 Jun

What makes criminals do what they do? Is a serial killer destined to perform his activities from birth, or did he develop his psychiatric abnormalities? Are some people just wired to be more aggressive than others? These are difficult questions and scholars have wrestled with them for decades. It’s the old nature versus nurture argument.

Most likely it’s a combination of the two. An individual might have a genetic makeup that makes him more prone to certain psychiatric or physical conditions but these might not develop unless he’s placed in an environment that nurtures that condition. For example, a child who is gifted with athletic prowess may never manifest that if he grows up where there are no athletic activities. A student blessed with a bright mind might never see that fully developed if his life conditions prevent him from achieving his academic potential.

Now comes a series of studies in which some scientists believe that the gene for aggression has been identified. It has been labeled the “Warrior Gene.” This is likely an unfortunate moniker for something that might indeed exist but not be quite as sinister as it sounds. Perhaps having a genetic makeup that promotes aggression was key to survival a few millennia ago. Of course nowadays, it can also create socially unacceptable behavior.

The gene in question has been labeled Monoamine Oxidase A, or MAOA. It has been found to exist in several variations with the MAOA-L variant being the one of concern.

First let’s look at what genes are and what they do. Our chromosomes are made up of long strands of DNA. Genes are simply sections of these chromosomes that have been coded to perform certain activities. For example, there are genes that regulate the production of insulin, others that dictate eye color, and still others that might determine whether we develop cancer or heart disease or other medical disorders.

Our DNA is simply an instruction manual. It tells certain enzymes within the cells to produce certain proteins. It is these proteins that carry out the functions. Such proteins are typically enzymes that then construct other proteins that do the work of keeping us alive. The enzyme might be responsible for constructing new liver cells, or producing antibodies to fight infections, or altering the chemistry of the brain.

It seems that MAOA is an enzyme that breaks down certain neurotransmitters within the brain: serotonin, norepinephrine, and dopamine. When a signal travels down a neural axon (the long tail of the neuron that makes up our nerve fibers) and is then passed on to the next neuron, it does so across a gap that we call a synapse. The electoral current comes down the axon and at the synaptic junction it causes the release of one of the above chemicals, which then passes through the gap and stimulates the neuron on the other side of the synapse. This neuron then sends the electrical current down its own axon where it will do the same when it reaches the next neuron in the chain. This is how electrical impulses are passed. An electrical-chemical transmission system. This is how we think. This is how we move our fingers. This is how our heart beats.

But if these chemicals are released into the synapse and they stimulate the next neuron, how do they know when to stop? That is, if the chemical is in the synapse why doesn’t it continue stimulating the neuron and cause a rapid fire sequence of electrical impulses within that neuron? The answer is, left to its own devices, that’s exactly what would happen. Here is where enzymes come into play. Enzymes like MAOA. These enzymes destroy these neurotransmitters very quickly so that only a single signal is passed along. This all happens in milliseconds. It happens every millisecond of everyday in all of us.

But what happens if the level of this destructive enzyme is low? Would the level of neurotransmitters increase within that person’s brain? Would this alter the way neural impulses travel through the brain tissue? Would this lead to alterations in the person’s behavior? They answer all of these questions is yes.

One of the variants of the MAOA gene is called MAOA-L. The L designation means that this variant gene causes a reduced production of the enzyme that destroys these neurotransmitters and this deficit allows the transmitter chemicals to build up within the synapses of these individual’s brains. And this build up just might result in altered behavior, in this case more aggressive behavior.

A group of Dutch women came to geneticist Hans Brunner at the University Hospital in Nijmegen to seek his help in understanding why so many of the men in their family were prone to severe acts of aggression, including rape and murder. To answer this question Prof. Brunner launched into a series of scientific experiments that ultimately led to the identification of the variant gene.

Of course, all is not that simple. There is no way to explain aggressive behavior by looking at a single gene anymore that it is possible to understand a symphony from a single note. Both are entirely too complex. However, this does raise some interesting questions, particularly to those writers who are interested in what makes our characters tick.

A few interesting articles: article

Brainethics Post

New Scientist article

Violence and the Brain


Posted by on June 15, 2010 in DNA, Medical Issues


6 responses to “Dangerous DNA: The Warrior Gene

  1. Devon Masarati

    June 16, 2010 at 4:28 am

    We teach our students about this at A level (12th grade and the year above). The interesting thing about this is that there are social effects as well. Anti social behaviour is observed in adults who have the variant form of the gene and have been abused/maltreated in childhood (12% of people committing 44% of crime). Adults who have the variant form and have not been maltreated are much less likely to have been arrested. There are some interesting details on the open learn website –


  2. Carol Kilgore

    June 16, 2010 at 5:43 am

    Fascinating. I love your blog because I learn so much here. Thanks for writing it.


  3. Kallum

    February 19, 2011 at 12:36 pm

    Hi who ever wrote this articl i wuz really amazed by it now i have a qestion how do you know if you have it?


    • D.P. Lyle, MD

      February 19, 2011 at 2:45 pm

      Since this is controversial and completely unproven on every level there is no need to test for this gene. It’s just an interesting little tidbit.


  4. a

    August 29, 2012 at 1:21 am

    I think there should be a test for people that want to know if they have this problem. Its not something that should be taken lightely. There are people out there who would possibly benefit from medications to help them with this problem of social effects and crimes.



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