1 / 59

CHAPTER 3 GENES, ENVIRONMENT, AND DEVELOPMENT

CHAPTER 3 GENES, ENVIRONMENT, AND DEVELOPMENT. Learning Objective. What do evolution and species heredity contribute to our understanding of universal patterns of development?. Species Heredity. Genetic endowment that members of a species have in common

nathaniel-brock
Télécharger la présentation

CHAPTER 3 GENES, ENVIRONMENT, AND DEVELOPMENT

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. CHAPTER 3 GENES, ENVIRONMENT, AND DEVELOPMENT

  2. Learning Objective • What do evolution and species heredity contribute to our understanding of universal patterns of development?

  3. Species Heredity • Genetic endowment that members of a species have in common • Reason that certain patterns of development and aging are universal • Examples • Walk and talk around 1 year of age • Sexual maturation from 12-14 • Wrinkling of skin in 40s and 50s

  4. Darwin’s Theory of Evolution • Species heredity explained by evolutionary theory • Main arguments of Darwin’s theory • There is genetic variation in a species • Some genes aid adaptation more than others do • Adaptive genes passed on more frequently • Evolution is about the interaction between genes and environment

  5. Modern Evolutionary Perspectives • Human development influenced by a shared species heredity that evolved through natural selection • Human development also influenced by cultural evolution • Humans inherit a characteristically human environment and learn methods of adapting to the environment • Cultural evolution is based on learning and socialization

  6. Learning Objectives • What are the basic elements and processes of individual heredity, including genes, chromosomes, formation of a zygote, mitosis, and meiosis? • What has the Human Genome Project contributed to our understanding of human development?

  7. Individual Heredity –The Genetic Code • Conception – new cell nucleus formed from genetic material of ovum and genetic material of sperm • New cell is the zygote • Each parent contributes 23 chromosomes, 46 total, organized into 23 pairs • Chromosomes - threadlike bodies in nucleus of each cell made up of genes

  8. Individual Heredity –The Genetic Code • Sperm and ova each have only 23 chromosomes because they are produced through the cell division process of meiosis • A reproductive cell (in ovary or in testis) splits to form two 46-chromosome cells • The two cells split again to form a total of four cells, each of which receives 23 chromosomes • In the female, results in three nonfunctional cells and one ovum • In the male, results in four sperm

  9. Individual Heredity –The Genetic Code • The single-cell zygote becomes a multiple-cell organism through the process of mitosis • A cell (and each of its 46 chromosomes) divides to produce two identical cells, each containing the same 46 chromosomes • Following conception, through mitosis, the zygote divides into two cells, then into four cells, then into eight cells, etc. • Mitosis continues throughout life

  10. Individual Heredity –The Genetic Code • Except for ova and sperm, all normal human cells contain copies of the 46 chromosomes received at conception • Both members of a chromosome pair influence the same characteristics • Chromosomes are strands of DNA • Deoxyribonucleic acid made up of sequences of adenine, cytosine, guanine, and thymine (A, C, G, and T) • Sequences are functional units - genes

  11. The Human Genome Project • Researchers mapped the sequence of the chemical units (A,C,G, and T) that make up the strands of DNA in a full set of human chromosomes • Human genome consists of genes that serve as a template for the production of particular proteins and DNA that regulates the activity of the protein-producing genes • 999 of 1,000 base chemicals are identical; only 1 of 1,000 accounts for human differences

  12. Learning Objectives • What factors account for genetic uniqueness? • How genetically similar are twins? • How is sex determined?

  13. Genetic Uniqueness and Relatedness • Genetic uniqueness of children of same parents due to crossing over, an aspect of meiosis • Before separation, pairs of chromosomes line up; when they cross each other, parts are exchanged • Crossing over increases the number of distinct sperm or ova an individual can produce

  14. Genetic Uniqueness and Relatedness • Genetic similarity of parent and child • An individual receives half her chromosomes and genes from her mother and half from her father • Genetic similarity of siblings • Siblings receive half their genes from the same mother and half from the same father, but meiosis determines the genes actually received • Siblings share half their genes, on average

  15. Genetic Uniqueness and Relatedness • Identical twins or monozygotic twins (or identical triplets, etc.) • Genetically the same • Result when one fertilized ovum divides to form two or more genetically identical individuals • Fraternal twins or dizygotic twins • Result from release of two ova and fertilization by two sperm • As genetically alike as siblings

  16. Determination of Sex • Of the 23 pairs of chromosomes • 22 pairs - autosomes • 23rd pair - sex chromosomes • In males, the 23rd pair consists of a long chromosome (X) and a short chromosome with fewer genes (Y) • Females have two X chromosomes • Fathers determine a child’s sex • If a sperm carries a Y chromosome, the XY zygote is a genetic male • If a sperm carries an X chromosome, the XX zygote is a genetic female

  17. Caption: Chromosomes in each cell consist of strands of DNA

  18. Learning Objective • How are genes translated into physical and psychological characteristics?

  19. Translation and Expression of the Genetic Code • Environmental influences combine with genetic influences to determine how a genotype is translated into a phenotype • Genotype • The genetic makeup a person inherits • Phenotype • The characteristics or traits that are expressed • Gene expression • Activation of particular genes in particular cells at particular times; guided by genetic influences and affected by environmental factors

  20. Learning Objectives • What are the mechanisms by which traits are passed from parents to offspring? • What is an example of how a child could inherit a trait through each of these three mechanisms?

  21. Mechanisms of Inheritance:Single Gene-Pair Inheritance • Single gene-pair inheritance • Pattern described by Gregor Mendel • Human characteristics influenced by one pair of genes (one from mother, one from father) • A dominant gene trait will be expressed • A recessive gene trait will be expressed only when the gene is paired with another recessive gene for the trait

  22. Caption: Can you curl your tongue?

  23. Mechanisms of Inheritance:Sex-Linked Inheritance • Sex-linked characteristics are influenced by single genes located on sex chromosomes • Actually X-linked because most attributes are associated with genes on the X • Y chromosomes are smaller and have fewer genes to serve as counterpart or to dominate • Example: if a boy inherits a recessive color-blindness gene on the X, there is no color vision gene on the Y to dominate the color-blindness gene

  24. Mechanisms of Inheritance:Sex-Linked Inheritance • A female who inherits a color-blindness gene usually has a normal color-vision gene on her other X chromosome that can dominate the color-blindness gene • If a female is to be color-blind, she must inherit the gene on both Xs • Hemophilia is another condition that illustrates the principles of sex-linked inheritance

  25. Caption: X-linked inheritance

  26. Mechanisms of Inheritance:Polygenic Inheritance • Traits such as height, weight, intelligence, personality, and susceptibility to cancer and depression are polygenic • Influenced by multiple pairs of genes interaction with environmental factors • Many degrees of expression are possible in polygenic traits • Traits tend to be distributed in the population according to the normal curve

  27. Learning Objectives • How do genetic mutations occur? • How do mutations affect development? • What are the most common chromosomal abnormalities? • When chromosomal abnormalities occur, how do they affect development?

  28. Mutations • Mutation • A change in gene structure or arrangement that produces a new phenotype • May be harmful or beneficial depending on their nature and the environment • Example: sickle-cell disease • Can be inherited by offspring

  29. Chromosomal Abnormalities • Chromosomal abnormalities occur when there are errors in chromosome division during meiosis • The ovum or sperm will have too many or too few chromosomes • Chromosomal abnormalities are the main source of pregnancy loss

  30. Examples of Chromosomal Abnormalities • Down syndrome or trisomy 21 • 21st chromosomes = 3 • Children have distinctive physical characteristics and typically are classified as having some degree of mental retardation • Associated with older age of parents

  31. Examples of Chromosomal Abnormalities • Chromosomal abnormalities that involve a child receiving too few or too many sex chromosomes • Consequence of errors in meiosis or damage from environmental hazards • Turner syndrome – a female born with a single X chromosome (XO) • Klinefelter syndrome – a male born with one or more extra X chromosomes (XXY) • Fragile X – one arm of the X is only barely connected

  32. Caption: Photo of X chromosome with fragile X problem

  33. Learning Objectives • What methods are used to screen for genetic abnormalities? • What are the advantages and disadvantages of using such techniques to test for prenatal problems? • What are some abnormalities that can currently be detected with genetic screening?

  34. Genetic Diagnosis and Counseling • Genetic counseling • A service that helps people understand and adapt to the implications of genetic contributions to disease • Carriers do not have the disease but can transmit the gene for it to their children

  35. Issues in Genetic Diagnosis and Counseling • Sickle-cell disease • Sickle-shaped blood cells cluster together and distribute less oxygen through the circulatory system • If parents are carriers of the recessive gene for sickle-cell disease • Have 25% chance of having a child with sickle-cell disease • Have a 50% chance of having a child who will be a carrier

  36. Issues in Genetic Diagnosis and Counseling • Huntington’s disease • Associated with a single dominant gene • Strikes in middle age and disrupts the nervous system • Child of a parent with Huntington’s disease has a 50% chance of developing the disease • Discovery of gene for Huntington’s on chromosome 4 led to a test that can reveal if a person has inherited the gene

  37. Learning Objectives • What methods do scientists use to discern the contributions of heredity and environment to physical and psychological traits? • What are the strengths and weaknesses of these methods? • How do scientists estimate the influences of heredity and environment to individual differences in traits? • How do genes, shared environment, and nonshared environment contribute to individual differences in traits?

  38. Genetic and Environmental Influences: Behavioral Genetics • Behavioral genetics • Study of the extent to which genetic and environmental differences contribute to differences in traits • Use heritability estimates • The proportion of all the variability in the trait within a large sample that can be linked to genetic differences among individuals • Variability that is not associated with genetic differences is associated with environmental and experiential differences

  39. Studying Genetic and Environmental Influences: Experimental Breeding • Selective breeding • Attempting to breed animals for a particular trait to determine whether the trait is heritable • Tryon bred maze-bright rats to demonstrate the influence of genetics upon maze-learning ability • Other animal breeding studies showed genetic contributions to activity level, emotionality, aggressiveness, etc.

  40. Studying Genetic and Environmental Influences: Twin, Adoption, and Family Studies • Twin studies • Studies of twins, both identical and fraternal, reared apart and together • Adoption studies • Are adopted children more similar to biological parents or to adoptive parents? • Family studies • Studies of siblings with different degrees of genetic similarity and varying environments

  41. Estimating Influences • Concordance rates • Statistical calculations to estimate the degree to which heredity and environment account for individual differences in a trait of interest • A trait is heritable if the concordance rates are higher for more genetically related than for less genetically related pairs of people • Correlation coefficients • Used when a trait (e.g., intelligence) can be present in varying degrees

  42. Estimating Influences • From correlations reflecting the degree of similarity between twins, behavioral geneticists can estimate the contributions to individual differences in emotionality from • Genes • Shared environmental influences • Common experiences • Nonshared environmental influences • Experiences unique to the individual

  43. Molecular Genetics • Analysis of genes and their effects • Useful in identifying the multiple genes that contribute to polygenic traits • Example: Alzheimer’s disease • Twin studies show heritability but the roles of specific genes have not been clarified

  44. Learning Objectives • How do genes and environments contribute to individual differences in intellectual abilities, personality and temperament, and psychological disorders? • What do researchers mean when they talk about the heritability of traits? • Which traits are more strongly heritable than others?

  45. Findings from Behavioral Genetics Research – IQ • Correlations highest in identical twins • Heritability of IQ is about .50 • Genetic differences account for 50% of variation in IQ and environmental differences for 50% • Genetic endowment appears to gain importance from infancy to adulthood as a source of individual differences in IQ • Shared environmental differences become less significant with age

  46. Findings from Behavioral Genetics Research – Temperament and Personality • Temperament • Tendencies to respond in predictable ways that serve as the building blocks of personality • Buss and Plomin (1984) reported average correlations of .50 - .60 between temperament scores of identical twins but scores for fraternal twins not much greater than zero • Conclusion: living in the same home does not generally make children more similar in personality • Shared environment influences are important but nonshared influences are more important

  47. Findings from Behavioral Genetics Research – Psychological Disorders • Schizophrenia • Concordance rate for schizophrenia in identical twin pairs is 48% and for fraternal twins the rate is 17% • 90% of children who have one parent with schizophrenia do not develop schizophrenia • This means that environmental factors contribute significantly • People inherit predispositions to develop disorders, not the disorder per se

More Related