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Gene-Environment Interactions

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

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Gene-Environment Interactions

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  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. Child’s Phenotype Gene-Environment CorrelationsThe Scarr and McCartney Model Child’s Genes Child’s Environment

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

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

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

  12. Gene-Environment CorrelationsThree 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 aboutGenotype-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

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