Chapter 3 Genes, Environment, and Development

1. 0 Chapter 3Genes, Environment, and Development

2. 0 Chapter 3: Genes & Environment • Species Heredity • Genetic endowment • Common to the species • Governs maturation and aging • Human examples • Two eyes, sexual maturity at 12-14 yrs. • Natural Selection: Genes allowing adaptation are passed on

3. 0 Evolution • Charles Darwin (1809-1882) • Species characteristics • How they change over time • Main Arguments • Genetic variation exists in all species • Some genes aid in adaptation • Kettlewell’s Moths: Genetic variability provides for adaptation

4. 0 Modern Evolutionary Perspectives • What we do today was adaptive for ancestors • Example: mothers invest more in child rearing • Maternity is certain; paternity may not be • Evolution: gene/environment interaction • Traits are demanded by environment • Advantageous genes for a particular environment survive

5. 0 Individual Heredity - The Genetic Code • Zygote: union of sperm and ovum • 23 pairs of chromosomes • Each pair influences one characteristic • Pair: One from father one from mother • Meiosis: produces sperm and ova • Mitosis: cell-division process • Creates new cells • Throughout life-span

6. 0 Genetic Uniqueness & Relatedness • Monozygotic (MZ) twins: 100% related • Single zygote divides • 2 genetically identical individuals • Dizygotic (DZ) twins: 50% on average • 2 ova fertilized by 2 sperm • Siblings: 50% on average • Parent & Child: 50% related, shared • Males: XY; Females: XX

7. 0 Translation of the Genetic Code • Genes provide instructions for development • Eye color and other characteristics • Regulator genes turn on/off gene pairs • Adolescent growth spurt • Shut down some in adulthood • Genotype: genetic makeup/potential • E.g., genes for tallness • Phenotype: actual/expressed trait (height)

8. 0 Mechanisms of Inheritance • Single Gene-Pair Inheritance • Dominant genes = dominant trait • Homozygous dominant • Recessive genes = ? Trait • Recessive trait if paired with another • Homozygous recessive genes • D trait if paired with a dominant gene • Heterozygous gene pair

9. 0

10. 0 Sickle-Cell Disease • About 9% affected in U.S. • Homozygous recessive (ss) • Heterozygous: (Ss) “carriers” • Can transmit gene to offspring • Incomplete dominance • Will not have the disease • May have sickling episodes

11. 0 Sex-Linked Inheritance • Single genes located on sex chromosomes • Actually X-linked • Males have no counterpart on Y chromosome • Females have counter on second X • Requires gene on both X’s for trait • Hemophilia, Colorblindness, Duchene MD

12. 0 Figure 3.2

13. 0 Polygenic Inheritance and Mutations • Polygenic: Most human characteristics • Height, weight, intelligence, temperament • Multiple pairs of genes • Normally distributed • Mutations: Change in structure/arrangement • Produces new phenotype • Sperm more likely than ova • Harmful or beneficial

14. 0 Chromosomal Abnormalities • Errors in chromosome division: Meiosis • Too many or too few chromosomes • Most spontaneously aborted • Down syndrome: Trisomy 21 • Physical deformities • Mental retardation • Related to age of parents

15. 0

16. 0 Figure 3.3

17. 0 Sex Chromosome Abnormalities • Turner’s syndrome: 1/3000 females • Single X chromosome (XO) • Small, stubby fingers, sterile • Klinefelter syndrome: 1/200 males • XXY, tall, sterile, feminine traits • Fragile X syndrome: mental retardation • Leg of X barely connected • Sex-linked: affects mostly males

18. 0 Genetic Diagnosis and Counseling • Tay-Sachs disease • Cause: recessive gene pair • European Jews/French Canadians • Huntington’s Disease • Single dominant gene • Learn about risk to unborn child • Learn about nature, inheritance and effects of genetic disorders in family history

19. 0 Behavioral Genetics • Genetic/environment cause of trait • Heritability estimates (genetic) • Methods of studying • Experimental and selective breeding • Tryon’s maze-bright rats • Twin, adoption, family studies • Reared together or apart • Concordance rates

20. 0 Figure 3.4

21. 0 Estimating Influences • Genetic similarity • Degree of trait similarity in family members • Shared environmental influences • Living in the same home • Nonshared environmental influences • Unique experiences

22. 0

23. 0 Accounting for Individual Differences • Correlations highest in identical twins • Genetic factors determine trait • Correlations higher if twins reared together • Environmental factors • Correlations are not perfect • Nonshared experiences • Identical twins more alike with age

24. 0 Temperament and Personality • Temperament correlations • MZ twins = .50 to .60 • DZ twins = 0 • Personality correlations similar • DZ shared environment unimportant • Same home - different personalities • Nonshared environment and genes important

25. 0 Psychological Disorders • Schizophrenia concordance rates • MZ = 48%: DZ=17% • Affected parent increases risk: 13% • Inherited predisposition • Environmental factors – triggers • Prenatal exposure to infection suspected

26. 0 Gene/Environment Correlations • E.g., Sociable genes • Passive G/E correlations • Parents create social home • Evocative G/E correlations • Smiley baby gets more social stimulation • Active G/E correlations • Child seeks parties, friends, groups, etc.

27. 0 Genetic Influences on Environment • Finding: Parents who read to their children have brighter children. Why? • Environment: reading to child makes them brighter • Genetic: brighter parents more informed or they enjoy reading themselves • Finding: Aggressive children have hostile parents. • Genetic: inherited behaviors • Environment: growing up with negative, hostile parents causes the behavior

28. 0 Controversies Surrounding Genetic Research • Identification of carriers of diseases and disorders • Giving information which leads to abortion • Experimenting with techniques for genetic alteration • Better parenting if child’s genetic predispositions understood