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Hereditary Influences on Development

Hereditary Influences on Development. Chapter 3. The Genetic Code. Chromosomes Rodlike Store and transmit genetic information Matching pairs 46 chromosomes, 23 pairs… Comprised of deoxyribonucleic acid, DNA. Gametes/Sex Cells. Sperm, ovum Contain only 23 chromosomes

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Hereditary Influences on Development

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  1. Hereditary Influences on Development Chapter 3

  2. The Genetic Code • Chromosomes • Rodlike • Store and transmit genetic information • Matching pairs • 46 chromosomes, 23 pairs… • Comprised of deoxyribonucleic acid, DNA

  3. Gametes/Sex Cells • Sperm, ovum • Contain only 23 chromosomes • Formed through meiosis • “Regular” body cells  mitosis • Sex cells  meiosis • Crossing over

  4. Multiple Offspring • Identical/monozygotic twins • Fraternal/dizygotic twins

  5. Patterns of Genetic Influence • Phenotype • Genotype • Can have same phenotype but different genotypes…why?

  6. How Are Genes Expressed? • Simple dominant-recessive inheritance • Each different form of a gene is called an allele • Alleles alike = homozygousAlleles different = heterozygous

  7. How Are Genes Expressed? • Dominant-recessive

  8. Examples of Dominant-Recessive GenesDominant Traits Recessive Traits Eye color brown eyes grey, green, hazel, blue Vision farsightedness normal vision normal vision nearsightedness normal vision night blindness normal vision color blindness* Hair dark hair blonde, light, red hair non-red hair red hair curly hair straight hair full head of hair baldness* widow’s peak normal hairline *sex-linked characteristic

  9. Examples of Dominant-Recessive GenesDominant Traits Recessive Traits Facial features dimples no dimples unattached earlobes attached earlobes freckles no freckles broad lips thin lips Appendages extra digits normal number fused digits normal digits short digits normal digits fingers lack 1 joint normal joints limb dwarfing normal proportion clubbed thumb normal thumb double-jointedness normal joints

  10. Examples of Dominant-Recessive GenesDominant Traits Recessive Traits Other immunity to poison ivy susceptibility to poison ivy normal pigmented skin albinism normal blood clotting hemophilia* normal hearing congenital deafness normal hearing and speaking deaf mutism normal – no PKU phenylketonuria (PKU) *sex-linked characteristic

  11. How Are Genes Expressed? • If heterozygous, can pass on a recessive allele to children • Carriers • Phenylketonuria (PKU)

  12. How Are Genes Expressed? • Sex-linked inheritance • Codominance • Polygenic inheritance

  13. Hereditary Disorders • Chromosomal abnormalities

  14. Hereditary Disorders • Autosomal abnormalities • Most frequent is Down syndrome (trisomy 21) • Mental retardation • Distinctive physical features • Mutations

  15. Detecting Hereditary Disorders • Amniocentesis • Chorionic villus sampling • Ultrasound • Know the procedures, advantages, and disadvantages of each…

  16. Genetic-Environmental Interactions • Reaction range

  17. Range of Reaction

  18. Canalization • Heredity restricts development of some characteristics • Examples = babbling, motor development

  19. Behavioral Genetics • The scientific study of how genotype interacts with the environment to determine behavioral attributes such as intelligence, personality, and mental health • Methods of studying hereditary influences • Selective breeding • Family studies • Twin studies • Adoption studies

  20. Behavioral Genetics • Twin studies • Identical/fraternal reared together • Adoption studies • Identical twins reared apart • Calculate concordance rates • Heritability coefficient

  21. Behavioral Genetics • Heritability coefficient (H) = (r identical – r fraternal) X 2 • Environmental influences • Nonshared environmental influences (NSE) • 1 – r identical twins reared together • Shared environment influences • 1 - (H + NSE)

  22. Behavioral Genetics • Anxiety scale score • Monozygotic twins: r = .78 • Dizygotic twins: r = .51 • Heritability: • 2(.78-.51) • 2(.27) • .54 • Nonshared: • 1 - .78 = .22 • Shared: • 1 – (.54 + .22) • 1 - .76 = .24

  23. Behavioral Genetics • Favorite color • Monozygotic twins: r = .26 • Dizygotic twins: r = .23 • Heritability: • 2(.26-.23) • 2(.03) • .06 • Nonshared: • 1 - .26 = .74 • Shared: • 1 – (.06 + .74) • 1 - .80 = .20

  24. Molecular Genetics • To discover the precise locations of genes that determine an individual’s susceptibility to various diseases and other aspects of health and well-being • Genome = complete set of instructions for making an organism • Human Genome Project

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