L11,12 Flashcards
What does MISTRA stand for?
Minnesota Study of Twins reared apart
Twins included in MISTRA study (# and age limit)
100 pairs, separated before 5 months and raised apart
Limitations (2) of Jim Twins
Confirmatory Bias
Remarkable similarities compared to other twins in study
DNA stands for
Deoxyribonucleic acid
Double helix of DNA contains 3 parts
Deoxyribose (sugar), phosphate, and base
4 types of base in DNA
Adenine, Thymine, Cytosine, Guanine
2 main functions of dna
replicate itself
direct synthesis of protein
Replication of DNA
double helix unzips separating the bases. These bases attract to their complements (creating 2 idential dna)
what is a gene
length of base sequence that codes for 1 protein chain
amino acid
organic molecules that link together to determine the shape and function of proteins
Genome
entire set of chromosomes (3.3 billion base pairs)
allele
alternate form of a gene. different characteristics
genotype
unique combo of indivs alleles
phenotype
observed characteristics- result of interaction b/w genotype and environment
Quantitative genetics goals (2)
1) estimating heritability of quantitative traits
2) est the influence of shares and non shared environment on quantitive traits
definition of heritability
proportion of total variance in the phenotype which is due to variance in the genotype
shared factors (quantative genetics) & non shared
shared: experienced the same by siblings in the same household (vary between families)
Nonshared : environmental factors experienced differently by siblings growing up in the same family. vary within families
heritability formula
h2= 2(r of mz-r dz)
variance not explained by genetics is comprised of what?
environment and measurement error
less reliable scales product __ heritability estimates (lower or higher)
lower
how is the equal environment assumption violated (2)
1) most (3/4) MZ twins share a common placenta and chorionic sac. DZ twins do not.
2) post natal environment- MZ twins may get treated more similarly than DZ twins. (however research disputes this- MZ twins still concordant when treated as DZ twins)
direct estimate of heritability study design
adoption study on identical twins
limitation of adoption study
fosters homes more homogenous than families at large
heritability estimates across twin and adoption designs for extraversion and neuroticism (most common studies)
50%, 40% neuroticism
studies to test contribution of shared environment (2)
mz twin adoption studies
non-twin adoption studies
mz twin adoption studies very similar on areas of MISTRA study, except 1 intell test? Raised together or apart had higher correlation?
WAIS. together, higher environmental influence
Twin study (together and apart) for Extra version and neuroticism. which was higher?
Twins raised together was higher for both, except in shields study
2 workhorses of quantitative genetics (nature, then nurture)
Twin
Adoption
adoption research says family resemblance is a result of Genes or Environment??
Genes
Types of non-shared environment factors (5)
1) Sibling interactions
2) Differential parental treatment (some evidence mothers treat siblings different- no correlation between maternal affection) may be effect of sibling difference (not cause)`
3) Family structure variables (birth order, sibling spacing)
4) extra familial experiences (Friends, sports, etc)
5) Major life events (accidents, trauma)
MZ differences Method- definition and what is it used for?
-Looks at twins raised together that are markedly different.
-to determine if non-shared environmental factors relate to behavioural outcomes.
2 ways genes and environments work together
1) Genotype- environment interaction, and correlation
Genotype- environment interaction definition
ppl with different genotypes respond differently to the same environment
example of genotype-environment interaction
DAT1 genotype AND maternal rejection contributes to depression (need both in combo)
3 types of Gen.Env. correlation
Passive
evocative
active
Passive Gen. environment correlation
parents passively provide genes and environment to foster genes
Evocative G.E. correlation
Indivs with genetic propensities evoke reactions from others. ie musically gifted children picked out for special opportunities
Active G.E. correlation
indiv w genetic propensities seek out environment to foster skills/genes
best method for detecting small single gene effects
allelic association method
allelic association method definition
compare allelic frequencies for groups of low-scoring and high-scoring indivs on a quantitative traits
example of allelic association
D4DR (dopamine transmission) and novelty seeking. long-repeat D4D4 alleles (less efficient at proecessing dopamine) seek novelty to increase dopamine release
