PSY2003 SEMESTER 2 - WEEK 1 Flashcards
define heritability
estimate of how much variance in some characteristic within some population is due to differences in heredity
what did Bouchard study in heritability
twin reared apart, gathered anecdotal evidence (ie, random similarity when talking to twins separately)
give an issue of what Bouchard studied in heritability
investigator bias = if look at enough components then will eventually find similarities (which are actually very insignificant)
instead of using anecdotes for studying heritability, what else can be done
using specific data on measures on big 5
found similarity for personality type, psychological interests
name issues of studying identical twins
modern study don’t usually include twins reared apart, so is hard to distinguish environment + genetics
even if raised seperate may be raised in similar families
name some conditions that showed 0.5+ correlation coefficients of heritability in MZ twin
ADHD, fatigue, depression, bipolar, autism, sz
summarise how heritability is calculated
compare correlation coefficient of identical, non-identicals for particular trait
heritability is twice difference between correlations for identical minus non-identical twins
what is equation for calculating heritability
Vp = A2 + C2 + E2
in equation of heritability what is V
variance of trait
in equation of heritability what is A
genetic component
in equation of heritability what is C
common/shared environment (anything in environment that make trait similar across pair)
in equation of heritability what is E
non-shared environment (anything in environment that make traits dissimilar across twin pairs)
what is heritability equation for an MZ twin
r=A2 + C2
what is heritability equation for an DZ twin
1/2A2 + C2
summarise what complexities with heritability may be
specific to a population where calculated and looks at variance between individuals
high heritability doesn’t imply environment doesn’t alter trait, particularly for individual
can change over time
If a group of individuals share a highly similar environment, what effect does this have on the heritability estimate of a characteristic?
heritability estimate will be high
if two environments are similar, then what can this look like in heritability calculations
may make it look like a characteristic heritability is higher, if dissimilar then can seem like it may be lower
depend on SES gradient = ie, in short distance in London reach many SES
summaries Multiplier Effect (Flynn)
if genetic or prenatal influence produce even small increase in some activity, early tendency will change environment in way that magnifies tendency
what is Flynn effect on heritability/multiplier effect
interacts with environments over time and makes it seem like its more heritable than actually it is
apply falling heritability estimates to smoking (Pinel)
genes don’t change however heritable components do still exist and no environmental ability to be expressed, so a fall in rates
define behavioural genetics
explain genetic and environmental contributions to human behaviour, via defining behavioural outcomes (phenotypes) and measuring corresponding genetic influences (genotypes)
define additive genetic influences (a2, or h2)
estimate of heritability, referring to causes of 2 siblings similarities as a result of additive genetic influence
define shared environmental influence (c2)
accounts for similarities between siblings not due to genetics. often refer to families environments, not always as can be other environment that sibling share (school and peers)
define non-shared environmental influences (e2)
unique environments, and situational/contextual factors making siblings different, including parental differential treatment, unique peer group, measurement error
what is biometric modelling
statistically estimate variance components + path coefficients
squaring standardised path coefficients give % of variance explained on specific traits
what are latent factors in biometric modelling
genetic and environmental contributions to phenotype of interest
state the 4 assumptions of biometric modelling
- equality in environments between sample comparison
- biometric modelling only account for addititve genetics
- assume no correlations/interaction btw/ genetic and environmental effects
- assume DZ share 50%
explain biometric modelling assumption of environmental equality
MZ actually treated more similarly than DZ, and so environment similarities more actually more genetic than environmental
how can environmental equality in between MZ/DZ twin be challenged in adoption study
adoptive parent has higher SES, marital stability, better mental health so shared environment effect minimised
however SES has little effect on adoptive-sibling correlations for drug use, IQ, delinquency
what characteristics does adoptive family SES have minimal impact for
little effect on adoptive-sibling correlations for drug use, IQ, delinquency
explain biometric modelling assumption of accounting only for additives
not all genetic influence adds = dominance and epistasis
outline additive genetics
effect of genome variations added up in different locations
summarise dominance
effect of 1 allele depending on other in same location in genome
summarise epistasis
effect of 1 allele on another but at multiple locations across genome
explain biometric modelling assumption of no correlation/interaction inbetween genetic and environmental effects is not right
actually 3 gene-environment correlations: evocative, active, passive
what is evocative GxE interaction
parent respond differently to child in same family due to different genotype
what is active GxE correlation
children actively seek out environments that fir their phenotypes
what is passive GxE correlations
parents genotypes influence both their own and child behaviour
biometric modelling assumes DZ twin share 50% - why may this have issue
just an average and can share 40-60% - variation can affect accuracy of biometric estimates
what is best ways to see if violation of assumptions of biometric modelling greatly influenced study results
- find if result replicated across variety of behavioural genetic designs (twin studies, adoption studies)
- mindful of concept of gene-environment interplay
- see if equal environment assumptions examined in each sample to see how much matters to specific phenotype of interest
- most psychological traits are additive but other genetic effects can also have relevance
apply shared environments for personality
account for almost no variance
apply shared environment to mental disorders
< 5% of variance is shared environment
comorbidity can be explained by additive genetic effect = suggest common genetic cause
suggest studying shared environmental effects in isolation isn’t best option but instead to study family effect, contributing to nonshared environmental variance
apply shared environment to IQ
moderate shared environment effect, with just being adopted increasing IQ, and greater IQ increase in high SES adoptive families
apply shared environment to behavioural traits (anti/prosocials)
significant correlations between adoptive siblings, with shared environments explained about 10% variance, implying modest shared environmental effects
name 2 complex analysis for quantitative behavioural genetic
decomposing correlations between family processes and child outcomes
gene-environment interactions
explain decomposing correlations between family processes and child outcomes (analysis of quantitative behavioural genetics)
variance of each phenotype broken into genetic +environ
so is covariance
allow estimation of environment x genetics mediations in association between 2 phenotypes
explain gene-environment interactions (analysis of quantitative behavioural genetics)
genetic sensitivity to environment, explaining why people who share same environmental experience have different consequences to events
GxE modelling detects if contributions of genetic, shared, nonshared environment components on some phenotype changes as result of including moderators in analysis
what is largest largest moderator of association between genetic and environmental contributions
age
in depression, what is more important (genetics/environment) regarding gender
significantly stronger additive genetic effects for females
but stronger shared environment effect in male
in SUD/antisocial behaviours, what is more important (genetics/environment) regarding locations
genetic effect stronger for SUD and antisoc beh in male adolescents in urban environment
but shared environmental effects stronger in rural environment
in conclusion, what factors are important on GxE interaction
age moderate genetic/environment influence for most trait (shared environmental effect decrease w/ age, genetic effect increase w/ age)
family relationship quality very important for shared environment contributions to traits (conduct disorders, adolescent SUD)
what do GWAS - genome wide association studies, do
examines specific genetic influence or effect of what varies within gene (allele)
alleles measured via studying SNPs (single-nucleotide polymorphisms)
GWAS study association between all or most SNP markers and phenotype of interest
collect SNP by DNA assay and compare
