Genetics & Behavior

9/10 Lecture Notes

The Human Genome

• DNA is the molecules that carries our genes

• DNA makes up who you are

• An Individual’s Unique Genome:

  • The more base pairs that are alike the more similar an individual is to another

• Very hard to link particular genes to a particular trait

Our Genes Affect Development By…

• Specifiying cells’ functions (from blood cells to neurons)

• Determining the production of proteins

• Turning certain cells on and off

Polygenetic

• Most human traits and behaviors involve more than two genes (POLYGENETIC)

  • Polygenetic: Controlled by more than two genes

• The more genes involved in a trait, the greater the range of variability across individuals

Says Who?: Behavioral Genetics

• Attempts to “measure” heritability of traits

  • Are people who share more genetic materials more like people who share less?

    • Essentially ttrying to address the “individual differences” and “nature/nurture” themes

• Behavioral Geneticists: Scientists, theorists who try to measure heritability of traits

Family Studies Used in Behavioral Genetics

1. Twin Study: Compare fraternal twins vs. identical twins all raised in same family as their twin

• THE LOGIC: Environment is controlled (nurture), the different is amount of genetic matieral (nature), so differences/similarities are likely to be attributable to genetics

2. Adoption Study: Compare adoptive parent/adopted child to bio parent/child

• THE LOGIC: Enviornment (nurture) is controlled; there is a difference in amount of genetic material so differences/simialrities are likely to be attributable to genetics

3. Adoptive Twin Study: Compare identical twins raised in same family versus identical twins raised in different families

• THE LOGIC: Amount of genetic material (nature) is controlled; difference in environment (nurture) SO differences/similarities are likely to be attributable to environment

Heritability Estimates

A measure of how much of the differences between individuals in a population are due to heredity

The Gene-Environment Interaction Model

Genotype = Our genetic material we inherited

Phenotype = Expression of our genotype. The actual, obsenate characteristics

Passive Effects

Direct transmission of genetic material and gene expression

Genotype/Parent —> Genotype/Child —> Phenotype/Child

The Norm of Reaction

The very same genotype can lead to different phenotypes depending on the environment

• Range of phenotype you can see given the genotype given the environment

• The “norm of reaction” is the range of phenotypes for a given genotype across the range of possible environments

Active Effects

Children shape their environment

• Active is when the child is shaping their environment

• Genotype/Parent —> Genotype/Child —> Phenotype/Child —> Environment/Child

Active Child Theme

Evocative Effects Treatment by Others

• Genetic traits elicit different behaviors, reactions, and treatment from people in their environment

Niche-Picking Environmental Choice

• Children select and attend to specific environments, activities, and niches that match their traits

Epigenetics

• Environment can alter genetic material

Genotype/Parent —> Genotype/Child —> Phenotype/Child; Environment/Child —> Phenotype/Child and Genotype/Child

• While DNA stays “fixed”, markers can be added to the genes (based on environmental experiences) that alter the genes and their expression and are passed onto the next generation

• In this way, your environment and life experiences can have lasting effects on the genotype

POINTS TO REMEMBER!

• Most traits are polygenetic and cannot be traced to a single gene

• Behavioral genetics teases apart genetic (nature) and environmental (nurture) contributions to development (be able to explain the way twin/adoption studies do this)

• The “Norm of Reaction” is the range of all possible phenotypes that a single genotype can express depending on the environment in which it develops

• An individual’s phenotype is a result of interactions between genetics and environment (know the model and understand the passive and active effects)