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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Chapter 3
Nature-Nurture
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Species Heredity
• Genetic endowment
- Species have in common
- Govern maturation and aging processes.
• Examples in humans
- 2 eyes, mature sexually at age 12 to 14
• Evolved through natural selection
- Genes allowing species to adapt passed on
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Evolution
• Charles Darwin (1809-1882)
- How characteristics of a species change over time
- How new species can evolve from earlier ones
• Main arguments
- There is genetic variation in a species
- Some genes aid in adaptation more than others
• Kettlewell’s moths (1959): Genetic variability
allows adaptation
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Modern Evolutionary Perspectives
• How what we do today was adaptive for ancestors.
- Ethology: Evolution of behavior in natural
environments
- Developmental psychobiology: Biology & environment
• Example: Mothers (~all mammals) invest more than
fathers in childrearing - maternity certain
- Adaptive mammalian male reproductive strategies
- Invest energy in few offspring – paternity certain
- Multiple partners/small investment – paternity uncertain
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Translation of the Genetic Code
•
Genes provide instructions for development of various
characteristics.
- Example: Eye color, or the development of neurons
•
Specific gene pairs turned on or off by regulator genes at
different times.
- Regulator genes responsible for adolescent growth
- Same genes shut down the action in adulthood
•
•
Genotype: Inherited genetic makeup (genetic potential for
tallness)
Phenotype: The characteristic/trait expressed (actual height)
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Mechanisms of Inheritance
• Single Gene-Pair Inheritance
- Dominant Genes: Dominant trait
- Recessive Genes:
- Recessive trait if paired with a similar gene
- Trait not produced if paired with a dominant gene
- Recessive Traits: Homozygous recessive genes.
- Dominant Traits: Dominant hetero-or homozygous
gene pair
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Single Gene-Pair Inheritance: Sickle-Cell Disease
• About 9% of Americans affected
- Homozygous recessive
• Heterozygous: Carriers
- Can transmit gene to offspring
- If both parents carriers: 25% chance
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Mechanisms of Inheritance: Sex-Linked Inheritance
• Single genes located on sex chromosomes
• Actually X-linked
• Males have no counterpart on Y chromosome
• Females have counterpart on second X
chromosome
- Requires gene on both X’s for trait
• Hemophilia, Colorblindness, Duchene MD
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Mechanisms of Inheritance: Polygenic Inheritance
• Most important human characteristics
- Height, weight, intelligence, temperament,
personality, sexual orientation, etc.
• Multiple (100s, 1000s) pairs of genes
- ~infinite combinations of genes leads to…
• Normally distribution of these characteristics
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Alternative Mechanisms of Inheritance: Mutations
• A change in structure/arrangement
• Produces a new phenotype
• Sperm more likely than ova
• May be harmful or beneficial
- Sickle-cell gene prevents malaria
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Chromosome Abnormalities
• Errors in chromosome division during meiosis
- Too many or too few chromosomes
• Most spontaneously aborted
• Down Syndrome: Trisomy 21
- Physical deformities
- Mental retardation
- Related to age of parents
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Behavioral Genetics
• Genetic/environmental cause of traits
• Heritability estimates (population estimates)
- % of variability in characteristic due to genetic var
• Experimental and selective breeding
- Tryon’s maze-bright rats
• Twin, adoption, family studies
- Reared together or apart
- Concordance rates
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Behavioral Genetics
• Studies reveal substantial heritability for
many physiological, psychological and
behavioral traits
- MZ correlations higher than DZ correlations
- Similar for reared together & apart
- Correlations higher for biological relatives
than for (adopted) family members
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Figure 3.4
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Behavioral Genetics
• DZ correlations typically less than 1.0
• Identical twins more alike with age
• Correlations higher if twins reared together
- Suggests that environment also plays a role
- Multiple types of environmental influence
possible
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Estimating Influences
• Genetic similarity
- Degree of genotype similarity
• Shared environmental influences
- Living in the same home, same parents, etc.
• Non-shared environmental influences
- Unique experiences
- Youngest v. oldest child, Parental favorite, etc.
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Estimating Influences
• Similar environments & experiences have
little impact & do not make us more alike
- Shared genes (NOT shared environ)
make us similar
- Non-shared environment makes us
different
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Individual Differences in Personality
• 40% genetic
• 40% environment (+ 20% error)
- Shared: 5%
- Non-shared: 35%
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Temperament and Personality
• Temperament correlations
- Identical Twins: .50-.60
- Fraternal Twins: 0
• Personality correlations similar
- Shared environment unimportant
- Non shared environment and genes important
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Nature & Nurture
• Reciprocal determinism
- Heritability < 1.0 revealing environmental influence
- Environmental influence interacts w/ genes in
development
- Genes -> environment -> genes & development
- Ex: genetic potential for intelligence interacts w/
enriched environment
- Genotype v. phenotype
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Figure 3.5
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Carol K. Sigelman, Elizabeth A. Rider
Life-Span Human Development, 4th Edition
Chapter 3: Genes, Environment, and Development
Gene/Environment
Interactions (correlations)
•
Passive:
- Inherited genes +
parents create environ
consistent w/ genes
•
•
Active
- Seek experiences
consistent with genes
Passive:
- Inherited genes + parents
create social environment
•
Evocative
- Smiley baby gets more
social stimulation
Evocative
- Genetically influenced
temperament evokes
different responses
•
Ex: Sociable genes
- Non-shared
•
Active
- Sociable child seeks social
activities
- Non-shared
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