Biological Beginnings
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Biological Beginnings






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Biological Beginnings Biological Beginnings Presentation Transcript

  • Chapter 2: Biological Beginnings Genetic Foundations Heredity & Environment
  • Evolutionary Psychology
    • Evolution is a theory.
    • Survival of the fittest does not necessarily imply evolution, only a healthy population.
    • Natural selection based on adaptability is a circular argument.
  • Evolutionary Psychology
    • Evolutionary psychology is not new.
    • Popular in the early 1900’s
    • 5000+ instincts were named
    • Proved to be a dead-end path
  • Evolutionary Psychology: Theory based on a theory
    • David Buss (1995, 2004)
    • Males and females of the human species evolved differently (e.g., spatial skills, sex)
    • Must assume that skills are inborn or that learning and experience changes genes in human gametes (egg/sperm)
    • Family curse
    • Feminists
  • Evolutionary Developmental Psychology
      • Theory based on a theory based on a theory.
      • Extended juvenile period evolved so that we could learn to cope with society.
      • Or did society “evolve” to cope with the juvenile period?
  • Evolutionary Psychology
    • Evolutionary Developmental Psychology
    • Human characteristics are not random. They are age and gender related.
    • Order and purpose are not related to random evolution, but imply the action of intelligence.
    • Part of the confusion has to do with teleology.
  • Evolutionary Developmental Psychology
    • Perspective here has profound effects on:
    • Concern for the tradition of learning/socialization
    • Judith Harris (Nature Assumption, 1998) says parents not important; genes and peers rule.
    • Views of the meaning of life
    • was man made for nature/society or nature for man
  • Genetic Foundations
    • DNA (deoxyribonucleic acid)
      • a complex molecule containing the genetic information that makes up the chromosomes
      • has two strands-forming a “double helix”- held together by bonds between pairs of nucleotides (spiral staircase)
    • Chromosomes
      • threadlike structures made of DNA molecules
      • that contain the genes
  • Genetic Foundations
    • Chromosomes
      • Human beings have 46 chromosomes (23 pairs)
      • Entire DNA code/set of chromosomes is repeated in each of the cells
      • Define the limits of species variation; separate species
  • Genetic Foundations
    • Chromosomes: limits
      • “ Each of us carries a “genetic code” that we inherited from our parents. Because a fertilized egg carries this human code, a fertilized human egg cannot grow into an egret, eagle, or elephant.”
  • Genes: Our Biological Blueprint
    • Genes
      • the biochemical units of heredity that make up the chromosomes
      • a segment of DNA capable of synthesizing a protein
    • Genome
      • the complete instructions for making an organism
      • Proteins are the cell building blocks and bodily process regulators
  • Genetics and Behavior Nucleus Chromosome Gene Cell DNA
  • Genes: Our Biological Blueprint
    • Human Genome Project
      • Completed about 2000
      • Humans have 20,000 – 25, 000 genes (21,667)
      • There are far more proteins than genes – 10-20 million
      • Genes (DNA) are dependent- collaborate with other sources of information
      • Gene expression/activity is affected by context or environment
      • Context is affected by hormones, light, nutrition, etc.
  • Genetic Foundations
    • 99.1% of DNA within the human race is identical
    • 98-99% of human and chimpanzee DNA is identical
  • Cell Division – Gamete Production
    • Mitosis (normal cell division) – the nucleus of the cell & the chromosomes duplicate and divide into 2 cells. Each has the same 23 pairs of chromosomes.
    • Gametes (sperm and ova) have only 23 chromosomes
    • They are formed by meiosis rather than mitosis.
    • At conception, these two unite resulting in a full complement of 46 chromosomes.
    • A fertilized egg is called a zygote.
    The Sex Cells
      • Alleles are normal variations of a gene, found at the same location.
      • A child who inherits the same allele (type of gene) from both parents is homozygous for that trait.
      • A child who inherits different alleles from each parent is heterozygous for that trait.
    Sources of Variation
    • Crossing over – chromosomes pair up and exchange segments during meiosis.
    • The probability of genetically identical, non-twin siblings is 1 in 700 trillion.
    Sources of Variation
    • Genetic Expression
    • Influenced by the environment
    • hormones
    • light
    • nutrition
    • behavior
    • stress (cortisol may cause a fivefold increase in DNA damage)
    Sources of Variation
  • Genetic Foundations
    • Genotype – genetic composition
    • Phenotype – observable characteristics
      • Patterns of Genetic Inheritance
      • Dominant-recessive: the dominant gene (allele) will determine the characteristic
    Sources of Variation
      • Patterns of Genetic Inheritance
      • Dominant-recessive: the dominant gene (allele) will determine the characteristic
    Sources of Variation
      • Examples of dominant genes
        • Dark hair, curly hair, dimples, types A & B blood (vs. type O), traits for normality in vision, hearing, pigmentation, etc.
        • Huntington’s Disease
    Patterns of Genetic Inheritance Dominant-recessive inheritance
      • Examples of recessive genes:
        • Cystic fibrosis, PKU, Tay-sachs disease. Sickle-cell anemia
    Patterns of Genetic Inheritance Dominant-recessive inheritance
      • Co-dominance: both alleles contribute to the phenotype
      • Additive: they contribute equally
      • Example of Co-dominance;
        • Sickle-cell anemia
    Patterns of Genetic Inheritance Co-dominance and Additive
  • X-linked or Sex-linked Inheritance
    • Humans have 23 pairs (46 total) of chromosomes – 22 pairs are autosomes; the 23 rd pair is XX in females and XY in males
      • Females - X chromosome from father to match the mother’s X
      • Males - Y from the father, does not have all the same genes
      • Defective gene on mother’s X is offset in females, but not in males
      • Examples: hemophilia, RG colorblindness
    Patterns of Genetic Inheritance X-linked (sex-linked) inheritance
      • Genes are chemically marked so that one member of the pair is activated regardless of its makeup.
      • Important whether the trait is inherited from the mother or father.
      • Examples: asthma, allergies, Huntington’s , diabetes
    Sex-linked Genetic Inheritance Genetic Imprinting
  • Patterns of Inheritance - Polygenic
    • Many genes interact to influence the characteristic
    • Most psychological characteristics are polygenic
    • (Where environmental factors are included, traits are said to be multi-factorial.)
      • Usually happen during meiosis
      • Involve breakage and failure to separate
      • Most common are Down syndrome (trisomy 21) (1 in 700-800 live births) and sex-linked
      • May be mosaic (not all body cells defective)
      • Often result in miscarriage
    Chromosomal Abnormalities
  • Chromosomal Abnormalities
    • Down Syndrome
    • Trisomy 21: extra copy of a chromosome on the 21 st pair
      • Round face, flattened skull, potruding tongue,extra fold of skin on eyelids, short limbs
      • Mental and motor retardation
    • More common to older mothers, rare among African Americans
      • Gene damaged on X chromosome
      • Most common inherited cause of mild to moderate mental retardation
      • Linked to autism
      • More common in males
    Chromosomal Abnormalities Sex-linked - Fragile X
      • XXY (Klinefelter) may have verbal difficulties. Tall, underdeveloped testes, possible breasts. 1/800 live male births.
      • XO (Turner) have trouble with math and spatial skills. Short and have webbed neck; may be infertile. 1/2500 live female births
      • XYY (Are they more aggressive, antisocial?)
    Sex Chromosome A bnormalities
  • Gene-linked Abnormalities
    • Over 7000 known (most rare), including:
      • Cystic fibrosis
      • Diabetes
      • Hemophilia
      • Huntington
      • PKU (phenylketonuria)
      • Sickle-cell anemia
      • Spina bifida
      • Tay-sachs disease
  • Genetic Counseling – for whom?
    • Family history of disease, mental retardation, physical defects
    • History of miscarriages
    • Mother over age 35 (rate of abnormality begins to rise sharply)
        • May cause miscarriage (except ultrasound, maternal blood samples)
        • Is the problem correctible?
        • Genetic engineering is still in the future.
        • Often the only decision is whether or not to abort the fetus.
    Prenatal Diagnostic Methods
        • Chorionic villi sampling (6-8 weeks);
        • detects genetic defects; risk of miscarriage, limb deformity
        • Amniocentesis – (11 weeks, best after 15 weeks); detects genetic defects; smaller risk of miscarriage
    Prenatal Diagnostic Methods
        • Fetoscopy – tube with light inserted into uterus; 15-18 weeks; limb & facial defects; some diseases & neural defects; some risk of miscarriage
        • Preimplantation genetic diagnosis –
        • Associated with in-vitro fertilization
    Prenatal Diagnostic Methods
  • Infertility
    • 1 in 6 couples in U.S.
      • Waiting too late
      • Sexually transmitted diseases
    • Fertility technology (IVF, donors)
    • Adoption
      • Babies culturally unavailable
  • Environmental Influence
  • Environmental Influence
    • Rats reared in an environment enriched with playthings show increased development of the cerebral cortex
    Impoverished environment Enriched environment
  • Environmental Influence
    • Culture
      • the enduring behaviors, ideas, attitudes, and traditions shared by a large group of people and transmitted from one generation to the next
    • Norm
      • an understood rule to accepted and expected behavior
      • norms prescribe “proper” behavior
  • Twins
    • Identical Twins
      • develop from a single fertilized egg that splits in two, creating two genetically identical organisms
    • Fraternal Twins
      • develop from separate eggs
      • genetically no closer than brothers and sisters, but they share a fetal environment
    Identical twins Fraternal twins Same sex only Same or opposite sex
    • Dizigotic (two zygotes)
    • Share approximately 50% of their genetic heritage like any two siblings.
    • Major causes are maternal age and fertility drugs.
    • Twinning dramatically on the increase since the 1970s.
    Multiple Births – fraternal twins
  • Multiple Births – identical twins
    • Monozygotic – one zygote (same fertilized egg)
    • Share 100% of genetic heritage
    • Occurs about 3 per 1000 live births worldwide
    • Factors may include temperature and oxygen levels and late fertilization
  • Genetics Research
    • Behavior Genetics
      • study of the power and limits of genetic and environmental influences on behavior
    • Molecular Genetics
      • subfield of biology that studies the molecular structure and function of genes
  • Nature-nurture Research
      • Molecular genetics
        • Human Genome Project
      • Behavioral genetics
        • Twin studies
          • Equal environment assumptions
        • Adoption studies
        • Concordance rates
  • Epigenesis – ongoing nature/nurture exchanges (bi-directional)
        • Reaction range
        • Canalization
        • Genetic-environmental correlation
          • Passive
          • Evocative
          • Active (niche-picking)