Genetics Flashcards
human genome
- refers to complete set of genes that an organism possess
- genome contains 30k-80k genes on 23 pairs of chromosomes
- small nb of genes = different for different individuals
Human Genome project
- designed to sequence the entire human genome
controversy
- behavioural geneticists attempt to determine the degree to which individual differences are caused by genetic and environmental differences
- concerns:
1. ideological concerns: no room for change; suggests plasticity is not present
2. concerns about renewed interest in eugenics
temperament vs trait
goals of behavioural geneticists
- % of individual differences ina trait that can be attributed to genetic differences/envrionmental differences
- ways in which genes and environment interact and correlate with each other to produce individual differences
- where in the “environment” environmental effects exist
T or F? Any trait that we still have has served an adaptive purpose
true
genotypic variance
refers to individual differences in the total collection of genes possessed by each person
phenotypic variance
refers to observed individual differences, such as height, weight, personality, etc.
heritability
proportion of phenotypic variance that is attributable to genetic variance
environmentality
proportion of phenotypic variance that is attributable to environmental variance
epigenetics
- effect of environment on gene expression
- silent gene becomes expressed; expressed gene becomes silent
heritability misconceptions
- cannot be applied to a single individual
- not constant
- not a precise statistic
nature vs nurture?
- no such debate at the individual level
- influences of genes and environment is only relevant for the discussion of group level variation
diathesis-stress model
selective breeding
- occurs by identifying the dogs that
possess the desired characteristic and having them mate only with other dogs that also possess the characteristic - Dog breeders have been successful precisely because many of the qualities they wish specific dog breeds to have are moderately to highly heritable
traditional behavioural genetic methods
- selective breeding studies
- family studies
- twin studies
- adoption studies
traditional behavioural genetic methods - selective breeding studies: advantages vs disadvantages
advantages:
- can infer heritability if selective breeding works
disadvantages:
- are unethical to conduct on humans
traditional behavioural genetic methods - family studies: advantages vs disadvantages
advantages:
- provide heritability estimates
disadvantages:
- violate equal environments assumption
traditional behavioural genetic methods - twin studies: advantages vs disadvantages
advantages:
- provide both heritability and
environmentality estimates
disadvantages:
- sometimes violate equal environments
assumption
traditional behavioural genetic methods - adoption studies: advantages vs disadvantages
advantages:
- provide both heritability and
environmentality estimates
- get around the problem of equal environments
assumption
disadvantages:
- adopted kids might not be representative of population
- problem of selective placement
selective placement
if adopted children are placed with
adoptive parents who are similar to their birth parents, then this may inflate the correlations between the adopted children and their adoptive parents
do MZ twins seem to be functionally more similar to each other than the environments experienced by the DZ twin?
No
twin studies
if a trait is highly heritable
- family members with greater genetic relatedness should be ore similar to one another on the trait than family members are less closely related
problem:
- members of a family who share the same environment influence the process
twin studies: assumptions
- equal environment assumption
- because parents provide both genes and environments to their children, and may provide more similar environments for identical than for fraternal twins, there is a potential compromise of the equal environments assumption - representativeness
adoption studies
genetic parents provide none of the environmental influences on their children, thus unconfounding genetic and environmental causes
contrast effect
- children try to be different from siblings
birth order effects
- each child experiences parents different
Falconer’s formula: calculting heritability
2 = 2(rmz - rdz)
refer to p. 168 of textbook
major statistical findings in personality
- heritability estimates for major personality traits of about 0.20-0.45
- some studies suggest as high as 48% across all 5 traits
- stability of these traits
major findings: attitude and preference
wide variance in heitability of attitudes
major findings: drinking and smoking
- behavioural manifestations of personality traits (sensation seeking, extraversion, neuroticism)
- drinking alcohol and smoking cigs are stable over time
- both show evidence of heritability
shared vs nonshared environmental influences
personality characteristics show heritability in 30-50% range
- hence showing substantial degree of environmentalism (50-70% range)
shared vs nonshared environmental influences: types of environmental influences
- shared
- in family environement, features of the environment shared by siblings
- e.g. nb of books in home - nonshared
- in family environment, features of the environment that differ across siblings
- e.g. teachers, friends
genotype-environment interaction
- differential response of individuals with different genotypes to the same environments (e.g. task performance of introverts vs extraverts in quiet vs noisy conditions)
- differential exposure of individuals with different genotypes to different environments
- genotype-environemnt correlations can be + or (passive, reactive, active)
passive genotype-environment correlation
- parents provide both genes and environemnt to children, yet children do nothing to obtain that environment
- e.g. child’s verbal ability and nb of books at home
reactive genotype-environment correlation
- parents (or others) respond to children differently depending on child’s genotype
- e.g. baby’s liking for cuddling and mother’s cuddling
active genotype-environment correlation
- person with particular genotypes seek out a particular environment
- high sensation seekers expose themselves to risky environments
