Genetic Explanations

Question 1

What is concordance rate?

Answer 1

the extent to which 2 people share genes

Question 2

What are monozygotic twins?

Answer 2

twins that share 100% of their genes

Question 3

What are dizygotic twins?

Answer 3

twins that share 50% of their genes

Question 4

What is the diathesis stress model?

Answer 4

genetic vulnerability + environmental stressor = condition or disorder

Question 5

What did Coccaro et al (1997) find about twin studies?

Answer 5

• found a concordance rate of 50% for MZ twins and 19% for DZ twins for aggressive actions
• found concordance rate of 28% for MZ twins and 7% for DZ twins for verbal aggression

Question 6

What was the research found for adoption studies?

Answer 6

• rhee and waldman (2002) conducted a meta analysis of adoption studies of direct aggression and antisocial behaviour: genetic influences were accounted for 41% of the variance in aggression
• hutchins and mednick (1975) found a significant number of adopted boys with criminal convictions had biological parents what convictions for criminal violence

Question 7

What is the MAOA gene?

Answer 7

• known as the ‘warrior gene’
• responsible for the production of an enzyme which allows the metabolism of neurotransmitters such as dopamine and seretonin
• a dysfunction in this gene can cause a abnormal activity of the MAOA enzyme which alters the brain’s neurotransmitters

Question 8

What are the different neurotransmitters and their effect on aggression?

Answer 8

dopamine - high - increases likelihood of feelings of reward when aggression is carried out
serotonin - low - lack of inhibition over impulsive behaviour
noradrenaline - high - overreaction to perceived threats

Question 9

What is research support for the MAOA gene?

Answer 9

Brunner et al (1993) -Studied 28 males of a large Dutch family who were repeatedly involved in impulsively aggressive violent criminal behaviour. The researchers found that these men had abnormally low levels of MAOA in their brains
Frazzetto et al (2007) - Found the association between low-activity MAOA gene and higher levels of anti-social behaviour only occurred in those who had experienced significant trauma during the first 15 years of life. Those with low MAOA-gene activity but no early trauma were not seen to have engaged in particularly high levels of aggressive behaviour

Question 10

AO3: research support into MAOA gene ✅

Answer 10

• Tiihonen (2015) studied 900 Finnish prisoners who had engaged in violent behaviour in the past
• each criminal was given a profile based on their offences which categorised them as violent or non violent and they were screened for low activity of MAOA and CDH13 genes
• the association between these 2 genes and previous behaviour was strongest for the 78 that fit the extremely violent offender profile