Biological Risk Factors Flashcards
Molecular Genetics
The study of the structure and function of genes at a molecular level
MAOA-L
The warrior gene, gene that breaks
-L variant has been linked with aggression and violence and is thought of as a genetic vulnerability
-occurs in 1/3 of the population.
-Associated with low IQ
-Gene is linked to the x chromosome; expressed more commonly in males
Behavioural Genetics
The study of relative power and limits of genetic and environmental influences on behaviour. There is no one gene that poses a risk factor, behaviour is determinant on the interaction of many different genes.
Inheritance
The process by which genetic information is passed on from parent to child
-Need to know the specific genetic endowment of an individual
Heritability (H2)
The proportion of the observed variance in a behaviour that can be attributed to genetic differences among individuals in a given population
-The relative importance of genetics vs. environmental contributions to the development of a specific trait or phenotype
-Examines individual differences at the population level
-Need to know the relatedness between individuals in a given population
How is heritability expressed?
h2 + e2 = 1
H2=0
Low heritability, most variable human characteristics have a non-zero heritability
If h2=0, any differences in the population for a specific trait are because of environmental differences within that population. If a trait has lower heritability, there needs to be environmental variance within the population.
-Having 1 arm, most people are born with both arms, and the loss of a limb is usually environmental
Shared environment
Aspects of the environment that are shared by all members of a family (SES)
-Shared environment contributes very little to the phenotypic variance in antisociality
-H2=0
Non-shared environment
Aspects of the environment that are not shared by all family members (different peer groups)
-Has more impact on the phenotypic variance in the environment. Most environmental influences that have a lasting effect on development are non-shared (differential pre-natal events, differential parental; solicitude, peers)
H2=1
High heritability, varies within a population
If h2=1, any differences in the given population for that trait are because of genetic differences within that population
-Intelligence has H2 of 0.7, this means 70% of the variance in intelligence for a population is because of genetic differences in that population
What happens if there is no genetic variance?
We cannot contribute genetic variation to the population, if genetic differences are going to explain the difference in a trait, there must be variance in the population for that trait.
Heritability estimates
A function of the environmental heterogeneity of a given population studied.
US and variance
The US has more environmental variance, socioeconomic status often defines the quality of your life.
-US would have a lower h2 factor because there is a greater opportunity for environment to impact behaviour
Inherited traits
A trait that is inherited is passed on through genes, it can therefore have high or low heritability
Traits that are not inherited
Has zero heritability
Inherited trait with no genetic variation
Has zero heritability
Binocular vision
Low heritability, low environment
Eye colour
High heritability, low environment
Intelligence
Both genetic (0.7) and environmental (0.3) variance.
-Has both plasticity and limits depending on genetics and environmental access
Having 2 arms
Low heritability, high environment
Personality Traits
High heritability in babies, environmental contribution is higher in adults.
-Ranges similar to intelligence and depends on the trait
Antisocial Behaviour
Genetic contribution .50
Shared environment .20 (most important when younger)
Non-shared environment .30 (most important when older)
Heritability is not..
-Not interpreted at an individual level, behavioural genetics are solely at the population level
-If aggression has a heritability statistic of .4, cannot say that 40% of someone’s aggression is due to genetics
How is heritability determined?
Estimate relative contributions of genes and environment by comparing concordance(matching) rates for a given trait between groups where the genetic relatedness is known
-Twin studies (MZ and DZ)
-Adoption studies
-Family studies
Twin studies
Examines concordance (matching) rates between monozygotic and dizygotic twins.
-Percentage of twins in each group that match on a given trait
-If concordance rates for MZ are higher than DZ, it is inferred that phenotypic traits that the study is examining has genetic contributions.
Why is it inferred that we have a higher h2 if the concordance rate between MZ twins is higher?
Monozygotic twins share 100% of the same genetic environment
What are the 2 paradigms of adoption studies?
-Parent-offspring adoption studies
-Sibling-offspring adoption studies
Parent-offspring adoption studies
Compare the concordance rate of the biological parent and child, and the concordance rate of the adoptive parent and child
-If concordance rate is higher for biological parent, genetic contribution is inferred
Sibling-Offspring Adoption studies
Compare the concordance rate between adoptive siblings, and biological siblings
-If concordance rate is higher for biological siblings, genetic contribution is inferred
Percentage of genes shared
MZ twins: 100
DZ twins: 50
Siblings: 50
Parents: 50
Grandparents: 25
Aunts and uncles: 25
Cousins: 12.5
