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Lecture 3

PSYB20 LECTURE 3.docx

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Department
Psychology
Course
PSYB32H3
Professor
Mark Schmuckler
Semester
Fall

Description
GENE-ENVIRONMENT INTERACTION Brian sessa orchestra - part of stray cats band (brian sessra) - modern rock - ended up forming new band infusing - specializies in xmas songs Gene-Environment Interactions (chapter 2 +3) he doesnt talk about it in class, but need to know it I. Introduction A. Behavior genetics B. Genotype and Phenotype II. Genes, the organism, and the environment A. What is a gene-environment interaction? B. Waddingtons cannalization principle C. Gottesmans 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 McCartney model 2. Three different gene-environment correlations a. Passive gene influences b. Evocative gene influences c. Active gene influences E. Questions about gene-environment interactions F. Is there a developmental program? G. Do genes determine the phenotype? H. Do genes determine capacity? I. Do genes determine tendencies? INTRODUCTION Behavior genetics Contributions of nature and nurture to human traits Polygenetic traits These are traits due to many genes, not a single one There is no single gene responsible for intelligence Researchers agree genes + environment are equally involved in all aspects Gene + environment interaction is strong, but how much of intelligence is from genes or from environment? Genotype and Phenotype Genotype Ones genetic endowment- individual genetic- what is encoded in your DNA Constant over lifetime- cannot change genotype Phenotype Observable characteristics of individual Phenotype = behavior A joint function of genotype + environment = phenotype Emerges through interactions with genotype and environment Focus on organisms as they develop GENES, 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 (white body fur, black nose, black feet and tail black) took out a patch of fur and put ice on it, grew back black, not white Studies of fur color Fur colour = phenotype and depends on temperature of environment TF black fur expressed itself when it was cold Temperatures at different places of the rabbits body How do we study gene-environment interactions? Keep environments of different genotypes constant (exact environment but changing genotypes- shows you genetic effects on development) Keep genotype constant while varying the environment (study phenotypes, differences are caused by environmental effects/influences on development) WADDINGTON canalization principle - tendency of heredity of genetic influences to restrict development of some characteristics to one of the small ranges of development - Behavior that is strongly canalized develops strongly in that environment 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 Infant development for which babies learn to walk, crawl or roll over, is relatively the same regardless of environment Language The time at which babies learn to babble is the same around 8-10 infants even deaf infants regardless of environment. Canalization and critical periods Some charactertics are canalized during critical periods ex: intellectual development that is strongly canalized in the 1 2 st years, but after that- intellectual development is divert st (more variable). Intellectual growth is highly canable in the 1 2 years of life, but then it ends and becomes variable. Implications of canalization Ensures child development under range of conditions Promotes survival RANGE OF RXN PRINICPLE Childest w/ greatest potential has the greatest rxn range Nature of the range has to do w/ the potential 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 they are in attribute(s) Monozygotic twins genetically identical Dizygotic twins, siblings genetically similar (fraternal twin) Have same degree of genetics (50% genetically similar) Half siblings You could study the kinship studies to fully understand the genetic aspects. No two people are truly living in the same environment even though you are living in the same environment.
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