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Biological Beginnings

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)