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Developmental Psychology - Chapter 2: Genetic and Environmental Foundations

Developmental Psychology

Agenda (1-21-2025)

  • Housekeeping item: Homework - read the textbook.
  • UIC Library.
  • Chapter 2 slides: Genetic and Environmental Foundations.

Learning Objectives

  • Describe the influence of nature and nurture on development.
  • Describe how genetics influences development.
  • Describe how the environment influences development.
  • Describe how studies of twins or adoptees can facilitate researchers' understanding of the relative influence of nature and nurture on development.

Genotype and Phenotype

  • Genotype: An individual’s unique genetic information.
  • Phenotype: An individual’s directly observable characteristics.

Genetic Foundations

  • Chromosomes: Store and transmit genetic information.
  • DNA: Substance of which genes and chromosomes are made.
  • Gene: A segment of DNA located along the chromosomes.

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

  • Monozygotic twins (Identical): One zygote that divides into two individuals.
  • Dizygotic twins (Fraternal): Two zygotes, or fertilized ova.

Alleles

  • Two forms of the same gene, one inherited from each parent, located at the same place on both chromosomes in a pair.
    • Homozygous: Both alleles are alike.
    • Heterozygous: Alleles are different.

Dominant–Recessive Inheritance

  • Only the dominant allele affects a child’s characteristics.
  • The recessive allele can be passed to children.
  • Many serious disabilities and diseases result from recessive alleles.

Example: Cystic Fibrosis (Autosomal Recessive)

  • Illustrates how recessive genes can lead to genetic disorders.
  • Probabilities:
    • 75% cystic fibrosis not expressed.
    • 25% cystic fibrosis.

Incomplete Dominance

  • Both alleles are expressed in the phenotype.
  • Results in a combined trait, or an intermediate between the two.
  • Example: sickle cell anemia.

X-Linked Inheritance

  • A harmful allele is carried on the X chromosome.
  • Males are more likely to be affected because the shorter Y chromosome lacks corresponding genes to override those on the X.
  • Example: hemophilia.

X-Linked Recessive Inheritance Diagram

  • Shows how an affected father and unaffected mother (or carrier mother) can pass on X-linked traits to their children.

Mutation

  • Sudden, permanent change in a DNA segment.
  • Can occur spontaneously or be caused by hazardous environmental agents.
  • Types of mutations:
    • Germline
    • Somatic

Polygenic Inheritance

  • Many genes affect each characteristic that varies among people, such as:
    • height
    • weight
    • intelligence
    • personality

Chromosomal Abnormalities

  • Down syndrome: Results when the 21st chromosome pair fails to separate during meiosis.
  • Sex chromosome abnormalities: Caused by problems with the X or Y chromosome, often not recognized until adolescence.

Risk of Down Syndrome

  • Figure 2.5 shows the risk of Down syndrome and all chromosomal abnormalities by maternal age.

Reproductive Choices

  • Genetic counseling
  • Reproductive technologies
  • Prenatal diagnosis and fetal medicine
  • Adoption

Genetic Counseling

  • Helps couples assess the risk of hereditary disorders and choose the best course of action.
  • Individuals likely to seek genetic counseling:
    • Couples who have had difficulties bearing children.
    • Known genetic problems exist.
    • Women over 35.

Social Issues: Health - The Pros and Cons of Reproductive Technologies

  • Donor insemination
  • In vitro fertilization
  • Surrogate motherhood
  • Ethical concerns:
    • Postmenopausal childbearing
    • Selection of desired characteristics; “designer babies”
    • Exploitation of financially needy women

Genetic Engineering

  • The purpose is to correct hereditary defects.
  • Human Genome Project:
    • Mapped sequence of all human DNA base pairs.
    • Working on identifying all genes and their functions.
    • Exploring new treatments, such as gene therapy and proteomics.

Adoption

  • Adoptees have more learning and emotional difficulties; possible causes:
    • Genetic predispositions
    • Stress of the biological mother
    • History of conflict-ridden family relationships
    • Adoptive parents and children are less alike
  • With sensitive parenting, most adoptees fare well.

Environmental Contexts for Development

  • Family
  • Socioeconomic status (SES)
  • Poverty/affluence
  • Neighborhoods
  • Schools
  • Cultural context

Family Influences on Development

  • Direct: Two-person relationships (e.g., parent, sibling, marital spouse).
  • Indirect: Third parties (e.g., a healthy marriage fosters effective co-parenting).
  • Adapting to changes within and outside the family (e.g., the birth of a baby).

Socioeconomic Status (SES)

  • An index that combines three related variables:
    • Years of education
    • Prestige of one’s job and skill it requires
    • Income
  • The first two measure social status; the last measures economic status.

Socioeconomic Status and Family Functioning

  • SES is linked to:
    • Timing of marriage and parenthood
    • Family size
    • Child-rearing values and expectations
    • Communication and discipline styles
    • Parents’ education and economic security
    • Children’s cognitive and social development

Poverty

  • 21 percent of U.S. children live in poverty.
    • Rates are higher for children of parents under age 25, ethnic minorities, and single mothers.
  • Risks of poverty:
    • Lifelong poor physical health
    • Poor cognitive development and academic achievement
    • Mental illness
    • Impulsivity, aggression, and antisocial behavior
    • Hostile family interactions

Affluence

  • Risks of affluence:
    • Poor academic achievement
    • Alcohol and drug use
    • Delinquency
    • Anxiety and depression
  • Unavailable parents:
    • Lack emotional closeness and supervision
    • Make excessive demands for achievement

Relationship of Eating Dinner with Parents to Youths’ Adjustment

  • Figure 2.6 shows the relationship of regularly eating dinner with parents to affluent youths’ adjustment problems.

Neighborhood

  • Offers resources and social ties that promote development.
  • Greater impact on economically disadvantaged.
  • In-school and after-school programs for low-income children show improved:
    • Academic achievement
    • Social adjustment
    • Family functioning and child-rearing

Schools

  • Complex social systems that affect many aspects of development.
  • Achieving well in elementary and secondary school is crucial to success in college.
  • Children in low-SES neighborhoods likely to experience poorer quality education.
  • Early intervention makes a difference!
  • Parental involvement aids academic achievement.

Cultural Context

  • Culture shapes all aspects of daily life.
  • U.S. culture emphasizes independence, self-reliance, and family privacy.
  • Subcultures have beliefs and customs that differ from the larger culture.
    • Example: Ethnic minority groups’ cooperative family structures foster resilience and enhance child-rearing.

Cultural Influences Example: The African-American Extended Family

  • Benefits:
    • Family members help with child rearing.
    • Strengthens family bonds
    • Transmits culture and heritage
    • Improves children’s school performance and social skills
    • Reduces stress of poverty and single parenthood, if present
    • Adolescent mothers are more likely to complete high school and get a job

Collectivism vs. Individualism

  • Collectivism:
    • Stress group goals over individual goals.
    • Value interdependent qualities: responsibility to others, social harmony, collaborative endeavors.
  • Individualism:
    • Primarily concerned with own personal needs.
    • Value independence: personal achievement, exploration, and choice in relationships.

U.S. Public Policy Shortcomings

  • Children and youth:
    • Lack of affordable health insurance and childcare
    • Weak enforcement of child support payments
    • High school dropout rates
  • Older adults:
    • Limited funding for social services
    • Social Security minimum is below the poverty line
  • Advocacy groups and research help improve policy.

Behavioral Genetics

  • Explores contributions of nature and nurture to the diversity of human traits and abilities.
  • Limited to investigating the impact of heredity on complex characteristics indirectly.

Heritability Estimates

  • Measure the extent to which individual differences in complex traits are due to heredity.
  • Obtained from kinship studies:
    • Examples: comparisons of twins, or adoptees and their biological parents.
  • Estimates range from 0 to 1.00.
    • 0.5 suggests heredity explains half the trait’s variation.
  • Limitations: may not represent the population; can be misapplied; limited usefulness.

Gene–Environment Interaction

  • Individuals respond differently to the same environment because of genetic makeup.
  • Similar responses can result from different gene–environment combinations.
    • Example: children with different environmental enrichment produce the same intelligence test scores.

Gene-Environment Interaction illustration

  • Figure 2.8 illustrates gene–environment interaction for intelligence by three children who differ in responsiveness to the quality of the environment.

Gene–Environment Correlation

  • Our genes influence the environments to which we are exposed.
    • Passive correlation
    • Evocative correlation
    • Active correlation: niche-picking

Epigenesis

  • Development resulting from ongoing, bidirectional exchanges:
    • Genes affect behavior and experiences.
    • Behavior and experiences affect gene expression.
  • Epigenetics studies how the environment alters gene expression, e.g., methylation.

Epigenesis Example: The Tutsi Genocide and Epigenetic Transmission of Maternal Stress to Children

  • Exposure to extreme adversity increases methylation of a gene integral to stress-hormone regulation.
  • Tutsi mothers pregnant during the genocide and their children tested 18 years later:
    • Both had significantly lower stress-hormone levels.
    • Long-lasting effects are evident in serious psychological disorders.
  • Prenatal exposure to severe maternal stress can induce epigenetic changes through methylation.