Genetics Flashcards
- Genetic similarities (MZ & DZ twins used to study genetic heritability)
Falconer model → calculate heritability of trait / behaviour from observed similarities b/w MZ & DZ twins by accounting for heredity, shared env, & individual env
What are DZ, MZ twins? Concordance rate higher for MZ twins = genetics
Gottesman & Goldsmith (1994)
Gottesman & Goldsmith (1994)
→ concordance rate of juvenile delinquency in MZ & DZ twins
→ 85 sets of young twins - likelihood of committing crime
→ 91% for MZ, 73% for DZ
→ genetics is a factor in aggression/delinquency but not 100%
Evaluation of Gottesman & Goldsmith (1994)
- TRIANGULATION → studied over 500 ADULT twins, 0.52 MZ, 0.23 DZ for criminality
- Large sample, significant results → generalisability
- EQUAL ENVIRONMENT ASSUMPTION
- Twin research not highly representative of general populace
- Genetic Similarities (DZ & MZ twins along with other types of kinship studies)
- Making comparisons based on genetic relatedness
- Drawing conclusions about genes & behaviour
Natsuaki et al (2009)
- Externalising antisocial problems in children (Whit, middle class)
- Longitudinal study, 390 sibling pairs, antisocial behaviours towards others
- MZ twins (0.59), DZ (0.21), then full, half, & genetically unrelated siblings
- Also found deviancy training (social learning) e.g. of environmental factor → behaviour of 1 could influence other
Natsuaki et al (2009)
- Longitudinal → same group of participants followed throughout entire study so less participant variables
- Developmental trends
- Did not identify a specific gene
- Issues w/ bidirectional ambiguity → correlation only
- No direct observational data → used a quantitative behavioural genetic design. May be able to pinpoint specific genes if DNA data collected
- Increased complexity in family structures = need to replicate findings w/ other samples
- Genetic Similarities & Genes (Counterclaim → environmental factors more impactful than genes)
Brendgen et al (2006)
→ teacher-rated reactive & proactive aggression in 6-year old twins pairs (172)
→ genes = 39% of variance for reactive, 41% of variance for proactive
→ rest explained by unique env. factors
→ aggression influenced by socialisation experiences specific to each type of aggression
- future studies aimed at isolating specific genes + env. variables
- Implications for preventative interventions → tailored to specific temperamental & socialisation needs of child
- Physical aggression only
- Other methods needed besides teacher ratings
- Parent ratings might be better - kids act dif at school
- research → genetic effects decrease w/ age, non-shared env. influences increases
- possible that heritable factors may play a larger role initially in placing a child at risk for reactively or proactively aggressive behaviour but that later socialisation experiences determine whether the child overcomes this risk
What is MAOA? (1st body paragraph of genes)
- MAOA functions in neuronal mitochondria
- regualtes levels of dopamines + serotonin
- in absence of sufficient levels of MAOA, neurotransmitters / hormones accumulate in neurons
- normal people = MAOA-H, others have MAOA-L
Meyer Lindenberg et al (2008)
- How differences in MAOA gene affects brain activity when exposed to threat
- fMRI, 1 group MAOA-H, MAOA-L, both shown angry / fearful faces
- MAOA-L = more activity in amygdala, less in vmPFC
- More emotional arousal (amygdala) & impulsivity (less activity in vmPFC) for MAOAL
- Low ecological validity + low operationalization of aggression
- Viewing only angry faces
- Lying in magnetic tube & not seeing real humans
- Didn’t account for other factors influencing aggression (e.g. testosterone)
- Only investigates 1 type of aggression (responsive)
Body paragraph 2 for Genes & Behaviour – environmental factors can influence expression on MAOA-L gene
Caspi et al (2002)
- interaction b/w MAOA & env = antisocial behaviour - over 1000 children, Dunedin (NZ), over 25 years (longitudinal) - MALES ONLY
- Sample genotyped, env. factors assessed (maltreatment)
- antisocial behaviour measured by clinical diagnosis of conduct disorder, personality checklists, official conviction records
- Participants w/ MAOA-l gene variant who were abused as children more likely to be antisocial + aggressive compared w/ just those w/ gene alone
Evaluation of Caspi et al (2002)
- High ecological validity + longitudinal
- Genetics & environmental interactions
- Low internal val since study did not take into account many confounding variables + major life events
- Partial cultural bias (NZ)
- Ethical considerations (assessed from birth) + stigmatisation
- Only focused on MALES → another study by -Sjoberg et al (2007) showed teenage females did not have the same effects
