1. Gene-Environment Interactions
Introduction
Behavior genetics
Genotype and Phenotype
Genes, the organism, and the environment
What is a gene-environment interaction?
Waddington’s cannalization principle
Gottesman’s Range Of Reaction principle
Genetic constraints on individuals
Problems with range of reaction
Kinship studies
Gene-environment correlations
Scarr and McCartney model
Three different gene-environment correlations
Passive gene influences
Evocative gene influences
Active gene influences
Questions about gene-environment interactions
Is there a developmental program?
Do genes determine the phenotype?
Do genes determine capacity?
Do genes determine tendencies?

2. Gene-Environment Interactions Introduction
Behavior genetics
Contributions of nature and nurture to human traits
Polygenetic traits
The question of “how much”
Genotype and Phenotype
Genotype
One’s genetic endowment
Constant over lifetime
Phenotype
Observable characteristics of individual
Emerges through interactions with genotype and environment

3. Genes, the Organism, and the Environment
Variations in any level of the environment can have an impact on the development of the organism
Experiments on the Himalayan rabbit
Studies of fur color
How do we study gene-environment interactions?
Keep environments of different genotypes constant
Keep genotype constant while varying the environment

4. Waddington’s canalization principle
Although both influence development, genes might influence some attributes more than others
Conrad Waddington
Canalization - Cases in which genes restrict development to a small number of outcomes
Ex, motor development and babbling
Canalization and critical periods
Implications of canalization
Ensures child development under range of conditions
Promotes survival

5. Range of Reaction Principle
Individual genotypes might operate in ways to restrict development or constrain outcome
Range of reaction principle:
Genotype, or genetic structure, sets the limits on the range of possible phenotypes that a person might display in response to different environments:
Example: Intellectual development in children

6. Range of Reaction Principle
Reaction Ranges A A B B C C

7. Range of Reaction Principle
Individual genotypes might operate in ways to restrict development or constrain outcome
Range of reaction principle:
Genotype, or genetic structure, sets the limits on the range of possible phenotypes that a person might display in response to different environments:
Example: Intellectual development in children
Generally, a statement about the interplay between environment and heredity
Problems with range of reaction principle
Issues in terms of how to investigate principle
Issues in terms of finding genetically identical individuals.
Kinship studies:
Studies in which members of same biological family compared to see how similar in attribute(s)
Monozygotic twins – genetically identical
Dizygotic twins, siblings – genetically similar
Half siblings

8. Gene-Environment Correlations The Scarr and McCartney Model
Child’s Genes
Child’s
Environment
Child’s
Phenotype

9. Gene-Environment Correlations The Scarr and McCartney Model, con’t
Child’s
Genes
Child’s
Phenotype
Parent’s
Genes
Child’s Environment

10. Gene-Environment Correlations The Scarr and McCartney Model, con’t
Child’s
Genes
Phenotype
Parent’s
Child’s Environment

11. Gene-Environment Correlations The Scarr and McCartney Model, con’t
Child’s
Genes
Phenotype
Parent’s
Child’s Environment

12. Gene-Environment Correlations Three types of correlations
Passive gene influences
Parents contribute to development in two ways:
Provide genetic material
Structure environment socially and emotionally
Because environments provided/created by parents depend on their genotype, environments will be generally matched to children’s genotype
Evocative gene influences
Child’s heritable characteristics affect behavior of others towards child
Active gene influences (niche picking)
Environments children prefer and seek out those that are most compatible with genetic predispositions

13. Environmental Influences on Gene Expression
Heredity as being prioritized
Canalization, range of reaction, gene-environment correlations
Driven by genetics
Problems with the supremacy of the genes
Bidirectional gene and environment effects
Genes affect behavior, and behavior effects genes
The epigenetic framework

14. Questions about Genotype-Environment Interactions
Is there a developmental program?
Analogy between genetic code and computer program
Do genes determine the phenotype?
Once genotype is fixed, phenotype is determined
Do genes determine capacities?
Genotype sets the absolute limits on the nature of the phenotype
Do genes determine tendencies?
Genotype determines a general tendency toward a particular phenotype
Example – the genetic contribution towards excitability is a tendency to get excitedv