Genetic explanation- Biological

• Genetic explanation

  • Genes consist of DNA strands.
  • DNA produces instructions for physical features like hair colour, eye colour and also physical features such as neurotransmitter levels and size of brain structures.
• How does the genetic explanation explain crime?

  Genetic explanations for crime suggest that offenders inherit a gene or combination of genes which predispose them to commit crime.
• Twin study

  • Christiansen (1977) studied 3500 twin pairs in Denmark and found concordance rates for offender behaviour.
  • 35% for monozygotic male twins and 13% for dizygotic male twins.
  • This included all twins in a region of Denmark between 1880 and 1910.
  • This indicates that offending behaviour and underlying predisposing traits are inherited.
• Adoption studies

  • Crowe, found that adopted children whose biological mother had a criminal record have a 50% risk of having a criminal record by the age of 18.
  • Whereas, adopted children whose biological mother didn’t have a criminal record only had a 5% risk.
• Candidate genes

  • Tiihonen et al, suggested that 2 genes (MAOA and CDH13) may be associated with violent crime.
  • Carried out a genetic analysis of 800 Finnish offenders.
  • Analysis found that 5-10% of all severe violent crime in Finland is attributed to MAOA and CDH13 genotype.
• What does the MAOA gene regulate?

  Regulates serotonin in the brain and has been linked to aggression.
• What does CDH13 link to?

  Substances abuse and attention deficit disorder.
• Adoption study

  • Midnick et al, study of 14,000 adoptees
  • Found that 15% of sons adopted by a criminal family went on to be criminals compared to 20% who biological parents were criminals.
• What issues are associated with twin studies?

  • The assumption of equal environments for both twins.
  • For example, it is assumed by researchers by studying twins, environmental factors are held constant because twins are brought up together and therefore must experience similar environments.
  • However, this shared environment assumption may apply more to MZ twins than DZ twins because MZ twins look identical and people tend to treat them more similarly.
  • The high concordance rates for MZ twins may be because they are treated more similarly than DZ twins.
• How does the genetic explanation provide support for the diathesis stress model for offending?

  • Mednick et al conducted a study on over 13,000 Danish adoptees, when neither the biological nor adoptive parents had convictions, the % of adoptees that did was 13.5%.
  • However when either of the biological parents had convictions this rose to 20% and when both biological and adoptive parents did it was 24.5%.
  • This shows that the genetic and environmental influence both have a role to play in offending behaviour.
• What problems are associated with adoption studies?

  • It is hard to separate genetic and environmental influences due to late adoptions.
  • Many adoptions take place when children are older, so have already spent several years with their biological parents.
  • This means that in the early and arguably most influential years, late-adopted children are still very much environmentally influenced by their biological parents.
  • Therefore this suggests that assessing the relative impact of nature and nurture may only be possible with early adoptions where contact with biological parents does not occur.