genetics AO1

• Twin studies

  • A researcher may compare the similarity between sets of MZ twins to the similarity between sets of DZ twins for a trait such as aggression
  • If they find that MZ twins are more alike in terms of traits, then this extra similarity is assumed to be due to genetic factors. (since MZ twins sharer 100% of the same DNA)
  • In humans, research has generally found that aggressive behaviours is more highly correlated in MZ twins than DZ twins
• Adoptive studies

  A second way of studying the influence of genetic factors is by studying children who have been brought up by parents who are not their biological parents. If researchers find a greater similarity in levels of aggression between adopted children and their biological parents, then this suggests an important genetic influence is at work. If they are like their adoptive parents environmental influences are important
• Selective breeding

  • The role for genetics in aggression has been conclusively demonstrated by the effects of selective breeding.
  • This is the process of choosing the animals with the desired characteristics in this case aggression.
  • The offspring showing the strongest sign of the desired characteristic are selected to breed
  • This has been shown in animals bred over many generations such as fighting cocks, pitbull dogs and spanish fighting bulls
• The MAOA gene

  • an enzyme that processes neurotransmitter such as serotonin.
  • MAOA-L is also called the warrior gene - this gene causes lower levels of the MAOA enzyme
  • lower levels of MAOA is associated with aggression
  • Brunner et al studied a family in the Netherlands. 5 members had a history of impulsive aggression and crime and the researchers found they ad dysfunctional MAOA genes, which resulted in a MAOA deficiency