Genes, environment and behaviour
- Genotype: Specific genetic makeup.
- Phenotype: individual’s observable characteristics.
- Alleles: alternate forms of a gene that produce different
Ex: free (recessive) or attached earlobes (dominant).1
- …study how heredity and environmental factors influence
- twins have a genetic heredity of 1; siblings .5%
- Family studies: compare family members. Study likelihood.
- Adoption studies: compare adopted children to adoptive parents and
- Twin studies: compare concordance rates for identical and fraternal
- Monozygotic twins: 1 egg & 1 sperm. Zygote separate. Indentical
- Dizygotic twins: 2 eggs & 2 sperm.
- IQ is quite heritable. (passed on)
- Heritability: Validation.
- Genotype, Shared environment & unshared environment = group
variation on a psychological trait.
- Estimates the proportion of trait variance due to genetic variance
within a group.
- Maximum value = 1.00 (100% of the variance)
1. Applies only to a particular group in a particular environment.
Environment vs genes
- Every trait has a reaction range
- Genetic traits have a range of possible phenotypes.
- There are individual differences in reaction ranges.
- Shared/unshared environments lead to differences in genetic
- Genetic characteristics influence the environmental factors that
children are exposed to.
- Genetic characteristics have an evocative influence. Characteristics influence the responses from others.
Genetics as a research tool
1. Knockout procedure
- Eliminate function of a specific gene
Ex: Leptin gene and obesity. One mouse is obese after they knocked
out the gene.
2. Knock-in procedure
- New gene of interest is inserted into animal.
Ex: Huntington’s disease. Motor abilities.
3. Linkage studies
- Take advantage of genes lying close together.
- Look for families with similar gene patterns.
- Evolution: Change over time in the frequency of occurrence of genes
in an inter-breeding population.
- Genes influence behaviour.