1 / 39

The Human Heritage: Genes and the Environment

The Human Heritage: Genes and the Environment. Nature/Nurture. First coined by Richard Mulcaster (1582) Refers to the ‘twin forces on development’ Biological and environmental influences Nature Inborn biological endowment Nurture environment within which development occurs

quynh
Télécharger la présentation

The Human Heritage: Genes and the Environment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Human Heritage:Genes and the Environment

  2. Nature/Nurture • First coined by Richard Mulcaster (1582) • Refers to the ‘twin forces on development’ • Biological and environmental influences • Nature • Inborn biological endowment • Nurture • environment within which development occurs • Interaction of Forces

  3. Sexual Reproduction and Genetic Transmission • Chromosomes • Single molecule of DNA, thousands of genes • 23 + 23 = zygote • Genes • segments of DNA, double helix, ladderlike • blueprint for synthesis of protein molecule • units of heredity

  4. Sexual Reproduction and Patterns of Heredity • The basics • somatic cells hold genetic info on copies of 46 chromosomes inherited at conception • Chromosomes dispersed throughout the nucleus • 23 pairs of chromosomes • 22 autosomes, 1 sex chromosome • males xy • females xx

  5. Cell Division: Somatic Cells • Mitosis • for somatic (body) cells • each cell replicates itself, then divides • result is two cells identical to original

  6. Cell Division: Germ Cells • Meiosis • for germ cells • replication with 3 processes to ensure resulting cell is nonidentical to germ cells (genetic diversity: chances are 1/70 trillion) • 2 steps of division • crossing over • random pairing during 2nd division • monozygotic vs. dizygotic twins

  7. Genotype/Phenotype • Genotype • the set of genes you inherit, your unique blueprint • Phenotype • how that set of genes is expressed as a result of the environmental stresses • the observable characteristics

  8. Environment • Genetic code is expressed in environments • Multi-levels of influence possible (egs.) • prenatal hormonal environment • chemical environment of the cell • nutrition of mother during pregnancy • stress of mother • opportunity for physical exercise • birth order as it relates to attention from parent

  9. Not Exactly Identical

  10. Mendel’s Laws of Inheritance • Definitions of terms • locus • homozygous • heterozygous • allele • dominant • recessive • intermediate expression of trait

  11. Laws of Inheritance • Discrete traits inherited on the basis of allele information from a single locus • Chin cleft • Blood type • Polygenetic traits inherited as result of information from several genes • Verbal skill • shyness

  12. Codominance: Result is distinct characteristics

  13. Genetic Sex also Source of Variability

  14. Sex Linked Genetic Effects:Red/Green Colorblindness • recessive trait • chances are 1/10 for males • chances are 1/100 for females • gene carried on x chrom, males have no complementary allele to compensate for the harmful effects

  15. Gene-Environment Interactions • Behavioral geneticists study how genes and environment combine to influence organism’s development • Variations in environment can have large effects on development of phenotype • Gene-environment interaction is a two-way process • Genetic factors play a role in the environments that individuals inhabit and how they shape their environments

  16. Range of Reaction: charting the change in phenotype as environment changes

  17. Canalization: some characteristics restricted to narrow range despite wide variation in environment

  18. Heritability: The study of genetic influences on behavior • Attempt to assess the degree to which variation among individuals on a given trait can be attributed to genetic as compared to environmental differences • e.g., weight - a physical trait • e.g., intelligence - a psychological trait • can factors in the environment influence weight or intelligence?

  19. Heritability, cont’d • Degree to which variation among individuals on a particular trait can be attributed to genetic differences • h2 = variation due to genes • total variation • applies to groups and not to individuals • for clones, any variation has to be due to environment, thus h2=0 • h2=1- variance accounted for by environment • heritability increases as genetic diversity increases and decreases as genetic diversity decreases

  20. Heritability: Infant Temperament • This video from the laboratory of Hill Goldsmith shows part of a study about infant temperament. An object of desire is set in motion, first for each infant in a pair of fraternal twins and then for each infant in a pair of identical twins. Note how the twins react when prevented from reaching the desired object.

  21. Heritability of Intelligence: History • Francis Galton’s Eminent Persons Study • tested idea that differences in intellectual achievement was due to genetic differences • basic flaw in logic is that eminent people also shared similar environment as well as gene pool • first to use adoptive method in study of boys adopted by RC Popes; found little evidence that environment affected eminence • Recommendations made for selective breeding, as they were to be made later by Hitler • Interesting aside: Darwin’s cousin

  22. Heritability of Intelligence: Kinship Studies • Twin Methods • correlations among IQs of pairs of people related to different degrees, e.g., identical twins, dizygotic twins, siblings, • Adoptive Methods • correlations among pairs of people who share an environment but not genes, e.g., adopted child and biological child

  23. Intelligence: The Findings • Identical twins raised apart .72 • Identical twins raised together .86 • Same sex twins raised together .62 • Diff sex twins raised together .57 • Siblings .47 • Unrelated siblings .30

  24. Heritability of Schizophrenia • Adoption Studies • e.g., Kety et al (1976) found strong evidence of heritability • only biological relatives of adoptee who is schizophrenic show high incidence of schizophrenia

  25. Heritablity of Schizophrenia • Twin Studies • High concordance for identical twins, this concordance deceases as genetic relatedness decreases • Identical twins 48% concordance • Fraternal twins 17% • Siblings 9% • Half-sibling 6% • Fisrt cousin 2% • Child of two sch. Parents 46% • Child of one sch. Parent 13%

  26. Mutations and Genetic Abnormalities • Mutations are errors in the process of gene replication; can be positive but usually negative • Down Syndrome (chromosomal error) • Phenylketonuria (PKU- defective recessive gene) • Klinefelter syndrome (sex-linked chromosomal abnormality) • Sickle-cell anemia (recessive gene)

  27. Chromosomal Errors • Most incompatible with survival • Variations in number sex chromosomes • Turner’s XO • Klinefelter’s XXY • XYY • Variations in number of other chromosomes • Down’s Syndrome, Trisomy 21 • Edward’s Syndrome; Trisomy 17

  28. PKU • Recessive gene disorder • causes excessive buildup of phenylalaline causing brain damage • environmental intervention (diet) can reduce effects

  29. Huntington’s Disease • dominant gene disorder • 50% chance of offspring inherit the disorder • 1/15,000 incidence • charcterized by severe mental and physical disorder • lag in onset of symptoms (35-45 yrs) accounts for continued occurrence • can be detected through genetic testing

  30. Biology and Culture • Cultural evolution can also account for existence of skills in a population • Innovations passed onto succeeding generations • Through processes of direct instruction, language, and demonstration • Little evidence of cultural evolution in other species • Meme: basic unit of cultural evolution

  31. Cultural and Survival • Some cultural tools may ensure survival • Hunting, gathering methods • Language • Child rearing practices (Quechuan babies)

  32. Coevolution • Two forms of evolution (cultural and biological) influence each other • Evidence that culture has influenced biology through the impact it has on reproductive advantage (e.g., tool use) • The problems of sorting out the nature-nurture influence

More Related