Genetics by Daniel Paynter https://padlet.com/daniel_paynter/tzjba889bn3t It is unlikely that researchers will identify a specific gene that causes aggression in humans. However, there are some “candidate genes” which are thought to lead to an increased risk of aggressive behaviour. en-us 2016-06-03 11:18:59 UTC 2026-01-22 20:59:18 UTC hello@padlet.com MAOA is an enzyme responsible for breaking down noradrenaline, serotonin and dopamine in the brain after they have transmitted impulses between cells. daniel_paynter https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596446 2016-06-03 12:52:10 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596446 ‐ Brunner et al (1993): This study examined a Dutch family which consisted of many males who displayed high levels of violence. The men were found to have low levels of MAOA, resulting in high levels of the 3 neurotransmitters MAOA controls. The men were subsequently found to have a defect in their MAOA gene. daniel_paynter https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596485 2016-06-03 12:52:30 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596485  This study does not consider the role of environmental factors in aggression. However, Brunner did acknowledge that genetic influences are not the sole cause of behaviour, and that there was unlikely to be a relationship between a single gene and aggression. ‐ This study casts doubt on the idea that low levels of serotonin cause aggression. daniel_paynter https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596511 2016-06-03 12:52:48 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596511 Twin Studies There are 2 types of twin: Mono zygotic (identical) who share 100% of their genes, and dio zygotic (non identical) who share 50% of their genes. If aggression were caused entirely by genetics, then for example, if one identical twin contracted a disorder, there would be a 100% chance of the other twin contracting the disorder (as identical twins share 100% of their DNA). However, research on aggression using twin studies has found: daniel_paynter https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596640 2016-06-03 12:54:00 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596640 ‐ McGuffin and Gottesman (1985): The study found an 87% link for aggression and antisocial behaviour in identical twins, and a 72% link in non identical twins. daniel_paynter https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596858 2016-06-03 12:56:13 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113596858 ‐ Coccaro et al (1997): After assessing 182 MZ and 111 DZ male twin pairs, the researchers concluded that genetics could explain 40% of the total differences in aggression, whilst the environment could explain 50% of the differences in physical aggression, and 70% of the differences in verbal aggression. daniel_paynter https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113597084 2016-06-03 12:57:32 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113597084 Adoption Studies Adoption studies compare children raised in adoption to their biological parents. If the children’s behaviour is more similar to that of their biological parents, we can say genes have a stronger influence on their behaviour. If the children are more similar to their adoptive parents, then environmental factors are more likely to have influenced their behaviour. daniel_paynter https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113597246 2016-06-03 12:59:12 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113597246 ‐ Miles and Carey (1994): This study was a meta analysis of 24 studies of the genetic basis of aggression. The researchers found that genetic influences accounted for 50% of the differences in aggression, and the influence of environmental factors increased with age. daniel_paynter https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113597477 2016-06-03 13:01:25 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113597477 nicole_snyman https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113773910 Moffit: Longitudinal study - 442 NZ males. Found a that those who had suffered abuse in childhood and had a low activity version of the gene were 9 times more likely to be aggressive and anti-social. - example of gene-environmental interaction.]]> 2016-06-06 10:48:57 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113773910 Cases: researched mice who were genetically engineered to lack MAOA. when they were adults, they were very aggressive when mating, suggesting that aggression is a result of MAOA deficiency. nicole_snyman https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113776219 2016-06-06 11:14:28 UTC https://padlet.com/daniel_paynter/tzjba889bn3t/wish/113776219