Genetic Factors Flashcards
Outline the MAOA gene
It’s an enzyme called Monoamine A
Role = ‘mop up’ neurotransmitters in brain after nerve impulse has been transmitted from one neuron to other
It does this by breaking down neurotransmitter (esp. serotonin) into constituent chemicals to be recycled/excreted. Production of this enzyme determined by MAOA gene.
Dysfunction in operation of gene may lead to abnormal activity of MAOA enzyme, which affects levels of serotonin in brain
Outline a variant of the MAOA gene
Nicknamed ‘warrior gene’
Leads to low MAOA activity in areas of brain & associated with various forms of aggressive behaviour
Brunner et al. (1993) studied 28 male members of large Dutch family repeatedly involved in impulsively aggressive violent crime like rape & assault
Researchers found men had abnormally low levels of MAOA in brain & low-activist version of it
Outline twin studies in genetic factors in aggression
Because MZ twins share 100% of their genes & DZ share 50%, we expect greater similarities in aggressive behaviour between MZ twins if aggression mostly influenced by genetic factors
Twins raised in same environment
For aggressive behaviour (assault) concordance rates of 50% for MZ & 19% for DZ
For verbal assault - 28% for MZ & 7% for DZ
Outline adoption studies investigating genetic factors in aggression
Rhee & Waldman (2002) conducted meta-analysis of adoption studies of direct aggression & antisocial behaviour - aggressive behaviour is prominent feature
Findings - genetic influence accounted for 41% of variance in aggression
More or less in line with findings of twin studies
Similar behaviours to bio parents = genetic influences
Similar behaviours to adopted parents = environmental influences
Outline gene-environment (GxE) interactions
Genes are crucial influences but they don’t function in isolation
Appears that low MAOA gene activity only related to adult aggression when combined with early traumatic life events
Frazzetto et al. (2007) found association between higher levels of antisocial aggression & low-activity MAOA gene variant in adult males, as expected
This was only case for those who xp significant trauma in first 15 years of life
Those who hadn’t xp trauma didn’t have particularly high levels of aggression as adults, even if they had low-activity MAOA variant
Evaluate the role of genetic factors in aggression
LIMITATION - Difficulty isolating separating genetic & environmental factors
E.g. - Individual may possess gene associated with aggression, but only expressed when triggered by environmental conditions
Ex. - McDermott et al. (2009) showed parties with low-activity MAOA gene behaved aggressively in lab-based money-allocation game, but only when provoked, otherwise no more/less aggressive than others
LIMITATION - Methods of measuring aggression
E.g. - Differ widely between studies, including self-reports, parent & teacher reports & direct observations
Rhee & Waldman’s meta-analysis found genetic factors had greater influence on aggression in studies using self-reports rather than parent or teacher reports
Ex. - If research findings vary depending on how aggression’s measured, it’s difficult to draw valid conclusions about role of genetic factors
LIMITATION - Multiple genetic influences (size of genetic effects statistically significant - also small
E.g. - This means there’s other genes involved in aggression
In study by Stuart et al. Intimate partner violence in men was not only associated with low-activity MAOA gene but also with serotonin transporter gene (5-HTT) which also influences serotonin activity in brain. It was combination of two genes most closely linked with IPV
