Overview
This lecture explores the basics of human genetics and how genes and environment interact to shape physical and psychological traits, with examples from genetic disorders and psychological research.
Principles of Evolution and Genetics
- Darwin's theory of natural selection explains survival and reproduction of organisms best suited to their environment.
- Sickle-cell anemia persists in some populations because carriers have enhanced immunity to malaria.
- Evolutionary psychology studies universal behavior patterns shaped by evolution over time.
- Behavioral genetics examines individual differences resulting from gene-environment interactions using twin and adoption studies.
Genetic Variation and Inheritance
- Chromosomes (23 pairs) are made of DNA and contain genes that control traits.
- Alleles are specific versions of a gene that determine trait variations.
- Genotype is an individual’s genetic makeup; phenotype is their observable traits influenced by genes and environment.
- Dominant alleles express their trait even if only one copy is present; recessive alleles require two copies.
- Traits can be monozygotic (single gene) or polygenic (multiple genes), like height and skin color.
- Mutations are permanent gene changes, sometimes harmful, sometimes beneficial for adaptability.
Human Diversity in Genetics
- Most genetic variation exists within racial groups rather than between them.
- Race has limited usefulness as a biological category in genetic research; focusing on ancestry is preferred.
Gene-Environment Interactions
- Range of reaction theory: genes set potential limits; environment determines where within those limits a person falls.
- Genetic-environment correlation: genes influence environment, and environment influences gene expression.
- Epigenetics studies how the same genotype yields different phenotypes due to environmental factors.
- Twin studies illustrate that identical genetics can lead to different outcomes based on experiences.
Genetics and Psychological Disorders
- Both genes and environment play roles in developing disorders like schizophrenia.
- High genetic risk combined with a disturbed environment greatly increases the likelihood of developing schizophrenia.
Key Terms & Definitions
- Genotype — An individual's complete genetic makeup.
- Phenotype — Observable physical or behavioral traits of an individual.
- Allele — A specific version of a gene.
- Dominant allele — An allele whose trait is expressed when at least one copy is present.
- Recessive allele — An allele whose trait is only expressed when two copies are present.
- Mutation — A permanent change in a gene.
- Polygenic — Trait controlled by multiple genes.
- Epigenetics — Study of how environments affect gene expression without altering the DNA sequence.
Action Items / Next Steps
- Review the differences between genotype and phenotype.
- Understand case studies on gene-environment interaction in psychological disorders.
- Prepare Punnett squares for predicting inheritance patterns.