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?

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

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

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

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

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

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

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

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

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

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

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

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

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