Chapter 2 – Genetic and Environmental Foundations

Genotype and Phenotype

• Genotype
  • An individual’s genetic information
• Phenotype
  • An individual’s directly observable characteristics
• Genetic Foundations
  • Chromosomes
    • Rodlike structures within the
      cells that store and transmit
      genetic information
  • DNA
    • Deoxyribonucleic acid, the chemical substance that makes up chromosomes
  • Gene
    • Segment of DNA along the
      length of the chromosome

Mitosis and Meiosis

• Mitosis
  • Process by which DNA duplicates itself
  • Produces new body cells containing the same genetic information
• Meiosis
  • Process by which gametes (sex cells) are formed
  • Halves the number of chromosomes normally present
  • Leads to genetic variability
• Autosomes, Sex Chromosomes, and Sex Cells
  • Autosomes
    • 22 matching pairs of chromosomes
  • Sex chromosomes
    • 23rd pair of chromosomes (XX = female, XY = male)
  • Gametes
    • Sex cells: sperm and ovum
  • Zygote
    • Formed when sperm and ovum unite

Twins

• Fraternal/Dizygotic
  • Result from release and fertilization of two ova
• Identical/Monozygotic
  • Result when a single zygote separates
    to form two individuals

Alleles

• • Two forms of the same gene, one inherited from each parent
    • homozygous (both alleles are alike)
    • heterozygous (alleles differ)
  • Occur at the same place on both chromosomes in a pair
• Dominant–Recessive Inheritance
  • Only the dominant allele affects children’s phenotypic characteristics
  • Carriers:
    • heterozygous (have one recessive allele)
    • can pass recessive trait to their children
  • Many serious diseases are product of recessive alleles

Incomplete Dominance

• • Both alleles are expressed in the phenotype
  • Possible results:
    • combined trait
    • trait that is intermediate between
      the two
  • Example: sickle cell anemia

Genomic Imprinting, Mutation, and Polygenic Inheritance

• Genomic imprinting:
  • chemical marker activates one allele in a pair
  • often temporary; may not occur in all individuals
• Mutation:
  • sudden, permanent change in a segment of DNA
  • may affect one or two genes, or many
• Polygenic inheritance:
  • characteristics influenced by many genes

Chromosomal Abnormalities

• Down syndrome: caused by problems with 21st chromosome
• Sex chromosome abnormalities:
  • caused by problems with X or Y chromosome
  • often not recognized until adolescence

Reproductive Choices

• Genetic counseling
• Prenatal diagnosis and fetal medicine
• Reproductive technologies
• Adoption
• Reproductive Technologies
  • Donor insemination
  • In vitro fertilization
  • Surrogate motherhood
  • New technologies

Genetic Counseling

• Helps couples
  • assess chances of hereditary disorders
  • choose best course of action in view of risks and family goals
• Recommended when
  • couple has had difficulties bearing children
  • known genetic problems exist
  • woman is over 35

Prenatal Diagnostic Methods

• Amniocentesis
• Chorionic villus sampling
• Fetoscopy
• Ultrasound
• Maternal blood analysis
• Ultrafast magnetic resonance imaging
• Preimplantation genetic diagnosis

Adoption

• Trends:
  • international adoption
  • adoption of older children
  • adoption of children with known developmental problems
• Children typically exhibit some difficulties, but most fare well

Environmental Contexts for Development

• Family
• Socioeconomic status and family functioning
• Neighborhoods, towns, and cities
• Cultural context
• Family Influences on Development
  • Direct influences
  • Indirect influences: effects of third parties
  • Adaptation to changes within and outside the family

Socioeconomic Status (SES)

• Social status:
  • years of education
  • prestige of one’s job and skill it requires
• Economic status: income
• Socioeconomic Status and Family  Functioning
  • timing of marriage and parenthood
  • family size
  • values and expectations for children
  • parents’ education and economic security
  • communication and discipline styles
  • investment in children’s cognitive development

Poverty: Who Is Poor?

• 46 million Americans (15%) are poor
• Those hit hardest are:
  • parents under age 25 with young children, especially single mothers
  • older adults who live alone, especially women
  • children, especially African-American, Native-American, and Hispanic children

Affluence: What Are the Risks of Affluence?

• • Alcohol and drug use
  • High levels of anxiety and depression
  • Unavailable parents:
    • lack of emotional closeness and supervision
    • excessive demands for achievement

Beyond the Family: Benefits of Strong Community Ties

• • Neighborhoods: resources and social ties that promote development
  • Towns and cities: mold children’s and adults’ daily lives
  • Small towns: promote connection and participation

Cultural Context

• Cultural values and practices: shape daily life within and outside the family
• Subcultures:
  • cooperative family structures help protect members from harmful effects of poverty
  • collectivism vs. individualism
• Public policies: laws and programs designed to improve current conditions

Extended Families

• Three or more generations living together
• More common in many minority cultures
• Benefits:
  • reduce stress of poverty
  • provide assistance for
    all generations
  • create strong family bonds

Individualistic and
Collectivist Societies

• Individualistic
  • People define themselves as separate entities
  • Independent self
• Collectivist
  • People define themselves as part of a group
  • Interdependent self

Behavioral Genetics: How Much Does Heredity Contribute to Behavior?

• Heretability Estimates
  • Obtained from kinship studies
  • Provide an estimate of proportion of individual differences in a trait attributable to heredity
  • Range from 0 to 1.00

Gene–Environment Interaction

• Individuals respond differently to same environment because of genetic makeup
• Similar responses can result from different gene–environment combinations
• Gene–Environment Correlation
  • Passive correlation
  • Evocative correlation
  • Active correlation: niche-picking

Epigenesis

• Development results from bidirectional exchanges between heredity and all levels of environment
  • Genes affect behavior and experiences
  • Experiences and behavior affect gene expression