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Unformatted text preview: Psych 101 07/10/2007 22:30:00 Chapter 5: Nature, Nurture, and Human Development Module 5.1: Genetics and Evolution of Behavior Genetic Principles o Chromosomes= strands of hereditary material o Genes= sections along each chromosome that control the chemical reactions that direct development o Dominant= a single copy of a gene is sufficient to produce its effect Recessive= a genes effects appear only if the dominant gene is absent o Recessive= the genes effects appear only if the dominant gene is absent o Sex-Linked and Sex-Limited Genes Chromosomes= determine whether an individual develops as a male or as a female A female has 2 X chromosomes, a male has one X and one Y The mother contributes an X chromosome and the father contributes an X or Y to the child Sex-Linked or X-Linked genes= genes located on the X chromosome Sex-Limited gene= occurs equally in both sexes but exerts its effects mainly or entirely in one or the other o Estimating Heritability in Humans Heritability= an estimate of the variance within a population that is due to heredity Ranges from 1 (heredity controls all the variance) to 0 (heredity controls none of the variance) Definitions of heritability includes within a population Estimates of heritability are misleading because we cannot fully separate the effects of heredity and environment Multiplier effect= a small initial advantage in some behavior, possibly genetic in origin, alters the environment and magnifies that advantage Studies of Twins Monozygotic twins= develop from a single fertilized egg and therefore have identical genes Dizygotic twins= develop from two eggs and share only half their genes, like brother and sister Studies of Adopted Children Resemblance to their adopting parents implies environmental influence Resemblance to their biological parents implies a genetic influence How Genes Influence Behavior o Direct and Indirect Influences Genes control maturation of brain structures, production of neurotransmitters, and production of neurotransmitter receptors Genes influence behaviors by altering body anatomy o Interactions Between Heredity and Environment Interaction= instance in which the effect of one variable depends on some other variable Temperament= the tendency to be active or inactive, outgoing or reserved, and to respond vigorously or quietly to new stimuli Phenylketonuria (PKU)= an inherited condition that, if untreated,...
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- Spring '08