Surprisingly, DNA is not completely understood.
WSJ.com - Science Journal
Life Events Thwart Scientists' Attempts To Draw DNA Profiles
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Now there is a glimmer of an explanation for why such “failures to replicate” are common in behavioral genetics: The same gene produces different traits in different people.Contrary to traditional understanding, genes don't lead inevitably to traits. Instead, says Darlene Francis of the University of California, Berkeley, scientists are discovering that “there is this intervening variable called life,” as she told the International Congress of Neuroendocrinology last month in Pittsburgh.
Life definitely intervenes between a gene called MAOA and the extreme aggression that researchers claimed it causes. In the late 1980s, a number of men in several generations of a large Dutch family were found to carry a mutation in the MAOA gene that made it inactive. They all had a long rap sheet of rape, attempted murder and arson. MAOA became known as the “violence gene,” headlines warned of “a violence in the blood,” and there was talk of screening everyone to identify carriers.
The link between MAOA and aggression made biological sense. MAOA breaks down brain chemicals, including serotonin. It comes in two forms, short and long. The short form, which about one-third of people have, can't do the breaking down as efficiently as the long form, disrupting the balance of neurotransmitters in the brain. The result was thought to be higher levels of aggression, as measured by a surge in activity in the brain's fear region -- the amygdala -- at the sight of an angry face. That might explain the hair-trigger tempers in that Dutch family.
In a study of 531 U.S. men, however, the violence gene didn't live up to its billing. When psychologist Stephen Manuck of the University of Pittsburgh analyzed men carrying the short form of the MAOA gene, he told the ICN meeting, only those who held antisocial attitudes, who received little parental affection as kids and whose fathers had low levels of education also had a history of aggression. Presumably, dad's low education is a marker for other traits, perhaps how he treats his kids.
Tags: DNA
