CHAPTER 2
NATURE WITH NURTURE
Chapter 2
How have ideas about nature and nurture changed?
What are genes? What exactly do they do?
What is the “environment”?
How do the genetic code and environmental contexts
interact in development?
PERSPECTIVES ON NATURE AND NURTURE
Development is driven by nature.
Development is driven by nurture.
Development is part nature, part nurture.
Development results from the interplay of nature and nurture
Nature vs. Nurture
• Dispute over the
relative importance of
hereditary and
environmental factors
in influencing human
development
Nature vs. Nurture
Nature
Nurture
• Heredity factors such as our
genes and chromosomes
that we receive from our
parents.
• Referred to as the
environmental factors—
how the child is brought up,
SES, etc.
DEVELOPMENT IS DRIVEN BY NATURE
• Preformationism
• Rousseau’s innocent babes
• Genetic determinism and
eugenics
DEVELOPMENT IS DRIVEN BY NURTURE
• The Blank Slate
• Locke’s view of the mind
“tabula rasa”
• Watson’s Behaviorism: strict
“fundamentalist” version of
environmentalism
DEVELOPMENT:
PART NATURE, PART NURTURE
• Heritability
• Degree to which different
traits are influenced by
genetic factors
• Twin studies
• Adoption studies
• Family relatedness studies
FIGURE2.2: HERITABILITY OF TRAITS IN TWINS
DEVELOPMENT RESULTS FROM THE INTERPLAY OF
NATURE AND NURTURE
• Contemporary view of relationship between nature and nurture
• Darwin’s Influence
– Theory of evolution
– Survival of the fittest and natural selection
• A gradual process of increasing complexity due to interaction between
heredity and the environment: http://www.5min.com/Video/LaurenceSteinberg-on-the-Nature-vs-Nurture-Debate-304230832
• Epigenesis: http://learn.genetics.utah.edu/content/epigenetics/twins/
The Genetic Code
•
•
•
•
•
DNA—the chemical that is the
basis for heredity
Chromosomes are strands of DNA
that carry genes, which are
smaller segments of DNA
The chromosomes are twisted into
a structure that looks like a long
spiraling ladder called a double
helix
The steps of that ladder are made
of pairs of chemical units called
bases
There are 4 bases that are the
“letters” of the genetic code:
–
–
–
–
A—Adenine
T—Thymine
C—Cytosine
G—Guanine
The Genetic Code
•
Genes are the units of heredity
•
Each gene is located in a specific
position on its chromosome and
has thousands of bases
•
The sequence of the bases tells
the cell how to make proteins that
enable the cells to carry out their
particular functions
Genotypes and Phenotypes
Phenotype—the observable (expressed) traits and
characteristics of a person
Genotype—your underlying genetic makeup which
contains both the expressed and the unexpressed traits
and characteristics
Sexual Reproduction
Mitosis
Meiosis
• Mitosis—the process through
which cells (other than
reproductive cells) divide
• Each resulting cell gets a full copy
of all 46 chromosomes
• Every cell in your body except the
sex cells (sperm and ova) has 23
pairs of chromosomes—46 in all
• http://www.youtube.com/watch?
v=Ba9LXKH2ztU&feature=related
• Meiosis—the process through
which gametes are produced
• Gametes are reproductive cells—
the sperm in males and the ova
(eggs) in females
• Meiosis produces cells with only
half a set of chromosomes
• Through meiosis each sex cell
ends up with only 23
chromosomes instead of 46 as in
mitosis
Sexual Reproduction
• Fertilization –2
reproductive cells
merge—mother’s and
father’s chromosomes
link
• Each person has 2 sets
of chromosomes and
so has 2 copies of
every gene—called
alleles
• http://www.youtube.c
om/watch?v=2cwXD6
QcNU&feature=related
What determines sex?
XX
XY
XX
Girl
XY
Boy
GENE-GENE INTERACTION
• Sex determination
• Additive heredity
–Child’s visible traits, phenotype,
is mix of mother’s and father’s
traits
• Dominant/Recessive
heredity
–One version of gene dominant
over another
• Regulator genes
–Some genes turn other genes
on and off
• Environmental influences
ECOLOGICAL PERSPECTIVE
• Bronfenbrenner compared
context of development to
Russian nested dolls.
• Microsystems –setting in
which individual interacts with
others face-to-face every day
• Mesosystem –ways in which
microsystems are connected
• Exosystem –contexts outside
the individual’s immediate,
everyday experience
• Macrosystem –larger forces
that define a society at a
particular point in time