Chapter 2

• Genotype:

  • Genetic endowment of a person
• Phenotype:

  • Observable characteristic
  • "Better" phenotype x environment = expression of genotype
• Behaviour geneticists study the influence of heredity and environment on individual differences in development
• Two principle ways of studying the relations between genes and environment:

  • Twin studies:
  • Mono vs. dizygotic twins
  • Adoption studies:
  • Discover whether the behavior and psychological characteristics of adopted children are more like their adopted parents or biological parents
  • Logic:
  • Degree of similarity correlates with genetic closeness, indicating hereditary influence
• Heritability:

  • Extent to which variation in a particular trait among individuals in a specific population is related to genetic differences among individuals
  • Determined by studying genetic differences among individuals in a population
• Three different types of gene-environment correlations:

  • Passive genotype-environment correlation:
  • Parents provide an environment influenced by their own heredity
  • Evocative genotype-environment correlation:
  • Children evoke responses from others based on the child's heredity
  • Active (niche-picking) genotype-environment correlation:
  • Children seek out environments that fit their genetic makeup
• Epigenetics:

  • Study of how the environment influences gene expression
  • Epigenesis: Development is the result of an ongoing bidirectional interchange between heredity and the environment
  • Epigenetic Inheritance:
  • Transgenerational transmission of molecular factors that determine how DNA is read and expressed
• Probabilistic epigenesis:

  • Theory of human behavior where different neural structures develop and activate based on an individual's biology or interactions with their environment
• Prenatal Development themes:

  • Germinal Period:
  • Fertilization to implantation
  • Cell division and differentiation
  • Blastocyst formation, implantation in uterine wall
  • Embryonic Period:
  • 2-8 weeks after conception
  • Rapid cell division, organogenesis (Endoderm, Mesoderm, Ectoderm)
  • Fetal Period:
  • Month 2 to birth
  • Growing and finishing phase, connection between muscles, organs, and nervous system
• Endoderm, Mesoderm, Ectoderm:

  • Endoderm: digestive system, respiratory systems
  • Mesoderm: circulatory system, muscles, bones, excretory system
  • Ectoderm: nervous system, sensory receptors, skin
• Three main events in neural development during the prenatal period:

  • Neurogenesis, synaptogenesis, myelination
• Teratogens:

  • Agents that can cause damage to babies
  • Principles of operation: Dose, Genetic susceptibility, Time of exposure
• Adverse effects of substances on development:

  • Thalidomide: Sedative causing deformities of arms and legs
  • Alcohol: Fetal Alcohol Spectrum Disorder (FASD), Fetal Alcohol Syndrome (FAS), Alcohol-related neurodevelopmental disorder (ARND)
  • Marijuana/Cannabis, Nicotine, Cocaine, Heroin
• Three stages of birth:

  1. Regular contractions, dilation, and effacement
  2. Pushing and crowning
  3. Birth of placenta (afterbirth)
• Apgar scale:

  • Assessment of newborn 1-5 minutes after birth
  • Evaluates heart rate, respiratory effort, muscle tone, skin color, reflex irritability
• Small-for-date infants:

  • Below expected weight given gestational age
  • More problems than pre-term infants
• Bonding:

  • Instantaneous strong feelings of affection for newborn
  • Not essential for social-emotional attachment in human infants
• Meiosis: form of cell division that occurs to form eggs and sperm (or gametes)
• Mitosis: Cellular reproduction in which the cell’s nucleus duplicated itself with two new cells being formed, each containing the same DNA as the parent cell
• Myelination: The process of insulating the axon with myelin sheaths. Increases the speed at which information travels through the nervous system