Mod 11

Introduction to Behavior Genetics

• Focus on how genetics and environment influence behavior and individual differences.

• Human cells contain chromosomes made up of DNA in a double helix structure.

• Genes are segments of DNA that dictate the development of proteins affecting individual development.

Chromosomes and Inheritance

• The human genome consists of 46 chromosomes in 23 pairs, with each chromosome containing specific gene locations.

• In males, X and Y chromosomes are unmatched due to missing genes on the Y chromosome.

• Each parent contributes half of their chromosomes to their offspring, creating genetic diversity.

Key Concepts in Behavior Genetics

• Behavior Genetics: Studies the power and limits of genetic vs. environmental influences on behavior.

• Hereditary: Refers to the transfer of characteristics from parents to offspring.

• Environment: Encompasses all non-genetic influences, including prenatal nutrition and cultural factors.

• Traits are polygenetic, influenced by multiple genes rather than a single gene determining traits like intelligence or personality.

Twin Studies and Findings

• Identical Twins (Monozygotic): Develop from a single fertilized egg, sharing the same genes.

• Fraternal Twins (Dizygotic): Develop from two separate fertilized eggs, sharing less genetic similarity.

• Studies show identical twins are more alike in personality and behavior compared to fraternal twins.

• Separated twins, whether intentionally separated or switched at birth, exhibit varying degrees of similarities, reinforcing the interplay of genetics and environment.

The Role of Adoption

• Adoption studies help distinguish between genetic relatives and environmental influences.

• Individuals raised apart from adoptive families often show greater similarities to their biological parents than to their adoptive parents regarding personality traits.

Temperament and Heritability

• Temperament: An individual's emotional reactivity, visible from infancy and persisting into adulthood.

• Heritability: The proportion of trait variation among individuals attributable to genetics. This does not indicate how much a specific trait is affected by a single gene.

• Nature (genetics) and nurture (environment) interact to influence behavior.

Important Twin Studies

• The 2015 study of Kelly twins, Scott and Mark, where Scott lived in space while Mark remained on Earth, showcased genetic and environmental interactions.

• The study aimed to understand how space conditions affect genes and behavior compared to those on Earth.

Molecular Behavior Genetics

• Molecular Genetics: Focuses on the molecular structure and functions of genes.

• Molecular Behavior Genetics: Studies how genes interact with environmental factors affecting behavior.

• Epigenetics: Examines how environmental factors influence gene expression without altering the DNA sequence, emphasizing the role of epigenetic markers.

Impact of Environment on Gene Expression

• Environmental factors influence gene expression through epigenetic modifications over a person's life, encompassing:

  • Prenatal: Exposure to drugs, toxins, and stress.

  • Postnatal: Neglect, variations in care, and emotional influences.

  • Juvenile: Social contacts and environmental complexity.

  • Adult: Cognitive challenges, exercise, and nutrition.

Ethical Considerations in Genetics

• Raises questions about the appropriateness of using genetic testing to select sperm, eggs, or embryos in fertility treatments.

• Epigenetic expression highlights how life experiences and environmental conditions can mark genetic influences over time.