Genetic factors in aggression Flashcards
What are genetic factors?
Inherited factors that increase or decrease the likelihood of behaving in a particular way
What is the concordance rate for aggression in MZ twins?
50%
What is the concordance rate for aggression in DZ twins?
19%
What do twin studies suggest about aggression?
It has a genetic basis as the MZ concordance rate is greater than the DZ concordance rate
In the adoption study looking at aggression, how many adoptions were studied?
14000
In the adoption study looking at aggression, what country was it conducted in?
Denmark
In the adoption study looking at aggression, what were the findings?
A significant number of adopted boys with criminal convictions had biological fathers with convictions for violence
In the meta-analysis of twin and adoption studies into aggression, how many studies were included?
24
In the meta-analysis of twin and adoption studies into aggression, what were the findings? (2)
Genetics can count for 50% of the variance in aggression + age plays a big role
What gene is associated with aggression?
The MAOA gene
What is the MAOA gene responsible for?
Producing an enzyme called monoamine oxidase
What does MAOA regulate?
The metabolism of serotonin in the brain
What are the 2 MAOA alleles?
MAOA-h and MAOA-l
Which MAOA allele is associated with aggression?
MAOA-l
What are the 4 AO3 points of genetic factors in aggression?
1) Research support for the MAOA gene
2) Problems with sampling
3) Difficulties with establishing the role of genetics
4) Can explain gender differences
In the MAOA family study, what nationality were the family?
Dutch
In the MAOA family study, what was the behaviour of the males like?
Highly aggressive + violent
In the MAOA family study, what crimes had some of the men been found guilty of?
Arson and rape
In the MAOA family study, what was found about the males genes?
They had defective MAOA genes
Which gene allele is prevalent in countries with a history of warfare?
MAOA-l
What percentage of people in countries with a history of warfare have the MAOA-l gene?
66.6%
What percentage of people in countries with no history of warfare have the MAOA-l gene?
33.3%
Name the 3 main reasons why it is difficult to establish a link between genetics and aggression.
1) More than one gene contributes
2) Many non-genetic factors that influence the manifestation of aggressive behaviour
3) These influences may interact with one another
Why is it an issue that research into the genetic factors in aggression are mainly focused on individuals convicted of violent crimes? (2)
1) Only a small minority of individuals who carry out violent attacks are convicted
2) Offenders designated as ‘violent’ on the basis of a court conviction are not necessarily the most serious, persistent offenders
What can the MAOA gene explain?
Gender differences in aggression
On which chromosome is the MAOA gene found?
The X chromosome
How many X chromosomes do females have?
2
How many X chromosomes do males have?
1
Why are males more likely to express the MAOA-l gene?
As the Y chromosome has no homologous region
Why are females less likely to express the MAOA-l gene?
As they have a second X chromosome, which may have a normal MAOA allele
