Human Genetics - Psychology 2e

Learning Objectives

• Explain the basics of evolution by natural selection
• Differentiate between genotype and phenotype
• Understand gene-environment interactions in physical and psychological characteristics

Introduction to Genetics in Psychology

• Psychological researchers study genetics to understand biological factors in behavior
• Humans share biological mechanisms but are unique in behaviors and reactions
• Key questions in genetics:
  • Why do disease outcomes vary among individuals?
  • How are genetic diseases inherited?
  • Are psychological disorders linked to genetics?

Sickle Cell Anemia: A Case Study

• Sickle cell anemia: red blood cells become crescent-shaped, clogging vessels, causing pain, fever, and damage
• Despite negative evolutionary effects, remains common among African descent due to malaria resistance
• Example Scenario:
  • Luwi (carrier) and Sena (non-carrier) both exposed to malaria
  • Luwi survives due to sickle-cell mutation; Sena succumbs to malaria

Evolutionary Perspective

• Theory of evolution by natural selection: organisms suited to environment survive and reproduce
• Sickle-cell carrier status advantageous in malaria-prevalent areas

Genetics and Behavior Perspectives

• Two fields: evolutionary psychology and behavioral genetics
  • Evolutionary Psychology: studies universal behavior patterns
  • Behavioral Genetics: studies individual differences via gene-environment interaction
  • Methods include twin and adoption studies

Genetic Variation

• Begins with egg and sperm each containing 23 chromosomes
• Genotype vs. Phenotype:
  • Genotype: genetic makeup
  • Phenotype: observable characteristics influenced by genotype and environment
• Dominant and Recessive Traits:
  • Dominant trait (e.g., cleft chin) expressed if allele from one parent is present
  • Recessive trait expressed if both alleles are recessive

Gene Mutations and Polygenic Traits

• Mutations: permanent changes in genes, can be harmful or beneficial
• Polygenic traits: traits controlled by multiple genes (e.g., height, skin color)

Human Diversity and Genetics

• Race is a weak concept in genetic research due to high intra-racial genetic variation
• Focus on ancestry instead of race for understanding human genetic diversity

Gene-Environment Interactions

• Range of Reaction: Genes set potential limits, environment influences actual potential
• Genetic Environmental Correlation: Genes influence environment; environment influences gene expression
• Epigenetics: Studies how same genotype can result in different phenotypes based on environmental factors

Link to Learning: Schizophrenia Study

• Study by Tienari et al. (2004): high genetic risk + disturbed environment heightens schizophrenia risk
• Shows necessity of both genetic vulnerability and environmental stress for schizophrenia development