behavioral genetics 2

large number of contributing loci, but affect of each locus is small and approximately equal - adding up over time

polygenic model

proportion of phenotypic variance accounted for by genetic differences

heritability

1.0 = (a^2 + d^2 + i^2) + (c^2 + e^2)

variance formula

what is p, or 1.0, in variance formula

phenotypic variance

what is a in variance formula

additive

what is d in variance formula

genetic dominance

what is i in variance formula

epistasis

what is c in variance formula

common environment

what is e variance formula

non-shared environment

quantitative methodology for studying inheritance of quantitative, multifactorial phenotypes

biometrics

____ _____ of a quantitative variance is assume to be an additive function of genetic and environmental components

biometric decomposition

twins with two placentas

dichorionic

twins with one placenta

diamnionic

are twins sufficiently similar to non-twins to support generalizability of findings? yes!

representativeness

is greater mz than dz twin phenotypic similarity attributable to their greater environmental similarity? no!

equal environments assumption

model that allows for an estimation of 3 components of phenotypic variance

falconer (ace) model

studies that provide converging evidence for twin studies and family studies, although they are hard to undertake

adoption studies

trying to place children with families who are similar in as many ways as possible to the natural parents

selective placement

prominent behavioral genetics study undertaken at UMN from 1979 to 2001

MISTRA

parents transmit genes that promote development of a specific trait are likely to create rearing environment that fosters development of that trait

passive g-e

our experiences can function as reactions our behaviors can elicit from others, to the extent that our behavior is genetically influenced

reactive g-e

our environment is a function of choices we make based upon our abilities and interests

active g-e

what from psychopathology is heavily implicated in gxe

diathesis-stress

what serotonin enzyme is known to cause aggression, with a negative correlation between it and 5-HT specifically?

mao-a

severe childhood maltreatment in those with low ___ led to great significant antisocial behavior later in life

mao-a

we assume gxe effects are…

uncorrelated

genes are not transmitted independently across generations if they are located near one another on the same chromosome

linkage

formal statistical procedure for investigating within-family associations between genetic markers and disease phenotypes

linkage analysis

general strategy geneticists use in early 2000s to identify genetic variants contributing to multifactorial risk

positional cloning

population-level association between alleles at linked loci

linkage disequilibrium

detected phenotypic variants are common, but must be ancient - since they're unlikely to be selected for.

GWAS

physical distance between loci and age of new mutation affect what?

ld strength

heritable diseases are relatively common but selectively disadvantageous

cd/cv model

population-level association between allele status and phenotype in case-control or population studies

allelic association

strengths of which kind of genetic approach: have high statistical power, and can test for involvement of a causal variant

candidate gene approach

weakness of which kind of gene approach: hypothesis driven, prone to false positives and p-hacking

candidate gene approach

weighted linear combination of SNPs identified in a large GWAS as being associated with disease risk

polygenic risk score (pgs)

genetic variants affecting risk for different diseases can substantially overlap

multifactorial

quantifies degree of genetic overlap for multifactorial phenotypes

genetic correlation

psychopathology is typically diagnosed ____, not based on ____

phenomenologically, etiology

for multifactorial diseases and phenotypes, there are likely thousands of contributing variants

polygenic

likely to have small to very small effects, likely to be regulatory rather than change protien product, and will require large samples to detect

common variants

small to large phenotypic effects, but only large effect variants are detectable. large effect variants are likely to change protien product, and will require special strategies to detect.

rare variants

even the largest GWAS lave much of the biometric heritability unaccounted for…

missing heritability

what are the likely sources of missing heritability

common variants of smaller effect and rare variants not captured in GWAS

3 ways to assess aggregate genetic effect

biometric heritability, polygenic scores, SNP heritability

for multifactorial phenotype, overlap in genes influences different phenotypes

pleiotropy

extensive evidence of ____ _____ implies pervasive existence of pleiotropy

genetic correlation

future of GWAS?

identify and inform therapeutic interventions and risk factors

all human behavioral traits are heritable

law 1 of behavioral genetics

shared family environment has minimal impact on individual differences in behavior

law 2 of behavioral genetics

non-shared environment exerts a major influence on individual differences in behavior

law 3 of behavioral genetics

shared environmental factors can exert ____ ____ on individual differences in personality

minimal influence

strong and pervasive, but hard to identify specific contributors. but, also has notable exceptions.

non-shared environmental influences

as you age, importance of shared environmental influences decline while genetic factors increase (for some traits)

wilson effect

how to populations differ genetically?

common and rare variants

differences in allele frequency due to drawing a sample from a large population. tend to be up to chance.

genetic drift

subset of a mother population reduces variability by chance

founder effect

catastrophic event wipes out most of mother population at random, reducing genetic variability. common example is ashkenazi jewish population

population bottleneck

common example of traceable local selection genetics

lactase persistence