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Chapter 2

Chapter 2. Section 4: The Genetic Contribution. Nature/Nurture Debate. How can heredity effect personality? Genes are made up of elements of DNA & they form chemical codes for the synthesis of protein The proteins affect virtually every aspect of the body

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Chapter 2

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  1. Chapter 2 Section 4: The Genetic Contribution

  2. Nature/Nurture Debate • How can heredity effect personality? • Genes are made up of elements of DNA & they form chemical codes for the synthesis of protein • The proteins affect virtually every aspect of the body • Genes affect personality through their effects on the brain & nervous system of an infant

  3. Measured by 2 Ways • Studying the temperament of infants & children • By doing hereditability studies of twins & adopted individuals

  4. Heredity & Temperament • Infancy • Differ in activity level, mood, heart rate responsiveness, & attention span • Born with genetically determined temperaments • Physiological dispositions to respond to the environment in certain ways • Quite stable over time

  5. Heredity & Traits • Estimate the heritability of specific traits within a group of children or adults • Favored by behavioral geneticists • An interdisciplinary field of study concerned with the genetic basis of behavior & personality • Heritability: A statistical estimate of the proportion of the total variance in some trait that is attributable to genetic differences among individuals within a group.

  6. Computing Heritability • Look at adopted children • Identical v. fraternal twins • Identical twins reared apart

  7. Twins • Identical (Monozygotic) Twins: • Develop when a fertilized egg divides into 2parts that develop into separate embryos • Fraternal (Dizygotic) Twins: • Develop when two separate eggs are fertilized by different sperm • They are no more alike genetically than any other pair of siblings.

  8. Twin Studies • Studying identical twins separated near birth is one behavior genetic method • Gerald and Mark met at age 31 after being separated at birth. • Both are volunteer firefighters • Like to hunt, eat Chinese food, and watch John Wayne movies • Drink the same brand of beer, with their hands held the same way (pinky curled)

  9. Evaluating Genetic Theories • Reasons for Caution • Not all traits are equally heritable or unaffected by shared environment. • Some studies may underestimate the impact of the environment. • Even traits that are highly heritable are not rigidly fixed. • Genetic predisposition does not imply inevitability

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