3.1

Chapter Three: Biological Psychology

3.1 Genetic and Evolutionary Perspectives on Behavior

Learning Objectives

  • 3.1a: Know the key terminology related to genes, heredity, and evolutionary psychology.

  • 3.1b: Understand how twin and adoption studies reveal relationships between genes and behavior.

  • 3.1c: Apply knowledge of genes and behavior to hypothesize why a trait might be adaptive.

  • 3.1d: Analyze claims that scientists have located a specific gene that controls a single trait or behavior.

  • 3.1e: Analyze explanations for cognitive gender differences rooted in genetics.

Genetic Editing Controversy

  • In November 2018, researcher He Jiankui announced he had edited the genes of human embryos to increase HIV resistance by altering the CCR5 gene using in vitro fertilization (IVF).

  • Ethical Concerns:

    • Immediate condemnation followed from the global scientific community.

    • Issues raised include unforeseen side effects of genetic alterations.

    • Ethical implications surround genetic enhancement (intelligence, athleticism, appearance) and accessibility for wealthy versus all individuals.

Biopsychosocial Model of Behavior

  • Behavior can be influenced by biological, cognitive, psychological, and social factors.

  • Understanding behavior requires considering the interplay of these factors while focusing on genetic and evolutionary explanations.

Heredity and Behavior

Genetic Influence on Behavior

  • Behavior is significantly influenced by genetic factors, just as physical traits are.

  • Genetics affect brain function, which in turn affects behavior.

The Genetic Code

  • Genetic Material: Located in the nucleus of human cells, organized into genes, which are responsible for protein creation that regulates bodily functions.

  • DNA Structure:

    • Formed in a double helix, composed of nucleotides: Adenine (A), Cytosine (C), Guanine (G), and Thymine (T), forming unique sequences that constitute genes.

    • E.g., gene sequences could be AGCCT, AAT, CGA, etc.

  • Genotype vs. Phenotype:

    • Genotype: Individual's genetic makeup (the set of genes).

    • Phenotype: Observable traits influenced by genotype and environmental factors (e.g., personality, intelligence).

Chromosomes and Alleles

  • Human genome comprises 23 pairs of chromosomes.

  • Each chromosome pair contains genes inherited from both parents.

    • Genes can have multiple forms (alleles), e.g., a gene may exist in a long form or a short form.

  • Homozygous: Identical alleles ( AA or aa)

  • Heterozygous: Different alleles ( Aa)

  • Gene expression affects trait visibility.

Phenylthiocarbamide (PTC) Sensitivity Example

  • Example of genetic influence on taste sensitivity:

    • Tasters possess at least one dominant gene (T), while non-tasters are homozygous recessive (tt).

    • Tasters typically report a bitter taste from foods such as Brussels sprouts which contain PTC.

Behavioral Genomics

Study of DNA and Behavior

  • Behavioral Genomics: Investigate the relationship between specific genes and behavior using molecular approaches.

  • Human Genome Project:

    • Completed in 2003, mapped approximately 21,300 genes.

    • Focused on understanding genes influencing brain development