GeneEnvironment Interactions I Introduction A Behavior genetics B

Gene-Environment Interactions I. Introduction A. Behavior genetics B. Genotype and Phenotype II. Genes, the organism, and the environment A. What is a gene-environment interaction? B. Waddington’s cannalization principle C. Gottesman’s Range Of Reaction principle 1. Genetic constraints on individuals 2. Problems with range of reaction 3. Kinship studies D. Gene-environment correlations 1. Scarr and Mc. Cartney model 2. Three different gene-environment correlations a. Passive gene influences b. Evocative gene influences c. Active gene influences III. Questions about gene-environment interactions A. Is there a developmental program? B. Do genes determine the phenotype? C. Do genes determine capacity? D. 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 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 Mc. Cartney Model Child’s Genes Child’s Phenotype Child’s Environment

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

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

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