Lecture 15 - Genetic Effects on Behaviour Flashcards
(37 cards)
What three main factors influence?
1) Inherited genetic material
2) Environmental experiences
3) Stochastic (random) developmental processes
What is meant by “stochastic developmental processes”?
Random biological and developmental events that contribute to individual behavioural differences, even in genetically identical organisms
What key finding came from studies on clonal fish by Bierbach, Laskowski, and Wolf?
Behavioural individuality occurred despite near-identical genetics and rearing conditions, indicating a role for stochastic processes
How do we know that genes influence behaviour in humans?
Through family, twin, adoption, and IVF studies, as well as research into genetic variants
How do animal studies support genetic influences on behaviour?
Via:
- Selective breeding
- Inbred strain comparisons
- Mutual effects
- The Russian Silver Fox Experiment
How does decreasing relatedness in family studies show?
A decrease in shared genetic material typically leads to reduced similarity in behaviour
What is the genetic similarity between monozygotic and dizygotic twins?
- Monozygotic twins share 100% of their genes
- Dizygotic twins share about 50%
What key principle underlies twin studies?
If behaviour is genetically influenced, more closely related individuals should be more behaviourally similar
What do adoption studies aim to separate?
Genetic vs. environmental influences on behaviour
What did Heston (1966) find in an adoption study on schizophrenia?
17% of adopted children with a schizophrenic biological mother developed schizophrenia vs. 0% of controls
What did the Danish adoption study reveal about schizophrenia risk?
13% of biological relatives of adoptees with schizophrenia had schizophrenia vs. 1% in controls
What does IVF research (Rice et al., 2009) reveal about genetic and environmental effects?
Associations between maternal smoking and antisocial behaviour were significant only when the mother was genetically related to the child, suggesting genetic mediation
How is heritability (H2) calculated using Falconer’s formula?
H2 = 2(rMZ - rDZ)
What is meant by “heritability” in genetics?
The proportion of variation in a trait within a population due to genetic differences
Can a highly heritable trait still be influenced by the environment?
Yes. High heritability does not mean environmental factors have no effect
How does environmental variability affect heritability estimates?
- Less environmental variation increases heritability
- More environmental variation decreases heritability
What did Mendelian randomisation (Mountjoy et al.) reveal about myopia and education?
Educational exposure may causally contribute to the development of myopia
Approximate heritability estimated? (autism, schizophrenia, bipolar disorder)
- Autism - 90%
- Schizophrenia - 80%
- Bipolar disorder - 80%
What is the ‘missing heritability’ problem?
The gap between heritability estimates and the known genetic variants that explain them
What may cause heritability?
- Undiscovered variants
- Overlooked sex chromosomes
- Epistasis
- Gene-environment interactions
- Methodolgical biases
What did Rutter (2002) conclude about genetics and behaviour?
Genetic factors play a substantial role in individual differences across all psychological traits
How are behavioural traits typically genetically structured?
Many variants of small effect and few of larger effect, interacting with the environemnt
Why is the concept of ‘a gene for…’ misleading?
Behavioural traits are polygenic and probabilistic, not determined by a single gene
What are the challenges in identifying behaviour-related genetic variants?
- Need large samples
- Consistent phenotyping
- Controlling for population stratification
- Establishing causality
