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CHAPTER 2
THE START OF LIFE: PRENATAL
DEVELOPMENT
STATEMENT OF INTENT
FOR THIS COURSE
Background
• I did not select this text
• This is the first time I’ve used it
• I apologize for the selection and for the author
This class is not a course in politics or religion.
Your grade in this class will NOT be based on
• Repeating my political views
• Repeating the author’s political views
• Anyone’s Ideology
To the extent possible, this course will be about Science.
The Science of human development. Therefore there will
be entire sections of chapters we will not cover.
STATEMENT OF INTENT CONT.
FOR THIS COURSE
The text contains considerable material which may be of
interest to various professions but does not seem to be a
part of developmental psychology.
Topics like IVF, government policy, testing, abortion, and
the like will not be covered in class as their connection to
development is tenuous.
Students with questions about this material may ask
questions in class or contact me outside of the classroom.
Let’s chat about what I’m leaving out. Do you get this
material in other classes?
My Observation on Observational Methodology
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Based on discussion w/ my spouse during our trip
Un(der?)-reported Observational Method Error
Author makes this error
Of course, “everybody knows”
that observational research is
People make this error
correlational but…
Behavior is observed
Behavior is recorded and reported
Behavior is ascribed to a cause.
However, the actual cause is
– Not observable
– Unknown based on observation
• Observation alone does not disclose causation
EARLIEST DEVELOPMENT
Beginning of Life
•Gametes from male and female join
– ovum
– sperm
•Fused gametes create zygote
•Resulting combination of their genetic instructions is
sufficient to begin creation of human life
Contents of a Single Human Cell
# changes fairly regularly
• Genes
– Specific DNA sequences
• Chromosomes
– Rod-shaped DNA
portions in 23 pairs
– Contain genetic blueprint
for individuals
– Replicate through
mitosis
Other Conception Mechanisms
• Think of reproduction at the cellular level as a kind of war
between reproducing organisms.
• Each “wants” to pass on the most information
• Females have advantage via the egg which contributes
all of an animal’s mitochondrial genes – well, usually
• Result:
– Ovum “selects” sperm to use
– Sperm “regulates” gene expression in the egg
Multiple Births: Two-or More-for the Genetic
Price of One
There are different kinds of multiple births
• Monozygotic
• Dizygotic
• Trizygotic and so on…
Causes of multiple births
• Fertility drugs
• Environmental agents?
• Racial, ethnic, and national (?) differences
• Family, e.g. inherited predilection
Rising Multiples
Lousy chart
Note nonlinear scale
Establishing the Sex of the Child
Also XXY and other
abnormalities
Mixing and Matching of Genes
Basics of genetics
• Dominant traits
• Trait that is expressed when dominant gene is present
• Expressed even if paired with a recessive gene
Notation uses a capital letter (B)
• Recessive traits
• Trait not expressed when a dominant gene is present
• Expressed only if paired w/ same recessive gene
Notation uses a lower case letter (b)
• Polygenic traits
• Expression controlled by multiple genes
• Complex gene interaction
• Neither Dominant or Recessive - like blood types (AB)
Just the right type
Genotype
Underlying genetic material but not outwardly visible.
Some genes “pair up” forming alleles – alternate forms
• Homozygous
• 2 similar forms of the gene (BB or bb)
• Heterozygous
• 2 different forms of the gene (Bb or bB)
Phenotype
Observable trait
Genetic Information Transmission
Cracking the Genetic Code
• The Human Genome
• National Human Genome
Research Institute
• http://www.genome.gov/
Humans less variable than any other primate.
Northern Europeans have Neanderthal genes.
Asians have Denisovan genes.
Africans have only human genes.
Highly
Misleading
Information from the Human Genome Project
& Private Research
Current Understanding of the Genetic Basis of
Some Disorders and Traits
When Development Deviates from the Norm
Causes
Genetics
Spontaneous
mutation
Environmental
insult
THE INTERACTION OF HEREDITY AND
ENVIRONMENT
Role of the Environment in Determining the
Expression of Genes: From Genotypes to
Phenotypes
Given behavior is not caused just by genetic factors; nor is
it caused solely by environmental forces
• Multifactorial transmission
• Genotype provides a range of possible outcomes
• Environment chooses a value in the range
• Some genotypes sensitive to environment
• Some genotypes unaffected by environment
• One example is stress of mother during pregnancy
Range of Possibilities: Determinants of
Intelligence
It is reasonable to believe that:
• Plasticity or sensitivity to environmental mitigation varies between individuals.
• Mitigation effects may have varying permanency.
• Mitigation effects may have ‘critical periods’.
Studying Development
How Much Is Development? How Much Is Nature?
Nonhuman animal studies
• Controlling genetics and environment
• Same genetics different environments
• Different genetics same environment
Human studies
• Adoption
• Identical & non-identical twins
• Twin studies
• Not without bias due to adoption agency placement policy
• Family studies
• Unrelated children same family environment
• Genetic similarity between parents and children
Do you have your mother's eyes?
And other lies about genetics found in textbooks
Family resemblances
• More genetically similarity  more likely to share
physical characteristics
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Obesity, blood pressure, respiration rates, age at death
Eye color
Myths of Human Genetics
Hair color
Required reading
Height
Muscle structure
And so forth
Nature, Nurture, and Intelligence
• Relative contributions of nature & nurture highly studied
• Relative contributions highly politicized
• Closer genetic link => higher relation of overall IQ scores
• Controversy over measurement methods
• Northeast vs. Southeast
• Race
• Immigrants
• Urban vs. Rural
Note: IQ is actually far more complex than a single score on a paper test.
Genetics and I.Q.
Do we inherit our personality?
Genetic and Environmental Influence on
Personality: Born to Be Outgoing?
Two* of “Big Five” personality traits
linked to genetic factors:
Neuroticism*
Extroversion*
Contentiousness
Openness
Agreeableness
What evidence supports this claim?
Psychological Disorders: The Role of Genetics
and the Environment
• Culture
• Parental encouragement
Can you think of any others?
Developmental Diversity
Can a culture's philosophical outlook be determined by
genetics?
Are there “good” and “bad” cultures?
Not Relevant
Mean Behavioral Scores for Caucasian American,
Irish, and Chinese 4-Month-Old Infants
The Genetics of Schizophrenia
Fundamental Principle
Within debate about relative influence of nature and
nurture
• Role of genetics is often to
• produce tendency toward future course of development
• Bound possible range
• Role of environment affects when and whether a certain
behavioral characteristic will actually be displayed
• Direct control
• Interactive control
Can Genes Influence the Environment?
Sandra Scarr suggests three ways child's genetic
predisposition may influence his or her environment:
• Active
• Passive
• Evocative
PRENATAL GROWTH AND CHANGE
Fertilization: The Moment of Conception
Germinal
Stages of Prenatal Development
• Germinal
– Fertilization thru implantation
• Embryonic
• Fetal
The Visible Embryo is a visual guide through fetal
development from fertilization through pregnancy to
birth. http://www.visembryo.com/baby/index.html
Stages of the Prenatal Period
Germinal Stage
Fertilization  two weeks
• Shortest stage
• During the first few cellular divisions, a zygote is properly called
a morula, or mass of cells.
• At 3 days zygote has 32 cells
• A zygote undergoes cellular division for four days.
• On the fifth day it forms a blastocyst.
• Blastocyst
• inner cell mass, or embryoblast, which forms the embryo
• outer layer of cells, or trophoblast, surrounds the inner cell mass
• fluid-filled cavity known as the blastocoele.
• The human blastocyst has 70-100 cells.
Germinal Stage Continued
Fertilization  two weeks
• Blastocyst continued:
• Travels to and implants in uterus
• Characterized by methodical cell division
• With division comes cell specialization
Embryonic Stage
2 weeks  8 weeks
• Organism firmly secures to uterus and is called an embryo
• Development of major organs and basic anatomy
Three distinct layers that forms different structures
• Ectoderm
• Endoderm
• Mesoderm
Body Proportions
Fetal Stage
8 weeks  Birth
• Formally starts when differentiation of major organs has
occurred
• Organism now called fetus
• Characterized by rapid development
– Organs become more differentiated and begin working
– Interconnections between body parents become more
complex and integrated
– Brain becomes more sophisticated
Note dissimilar scales making comparisons confusing
Older Women and Risks of Pregnancy
Threats to Development
Prenatal environment: Enter at your own risk!
• Teratogens
• Recreational Drugs: Heroin, Cocaine, and Crack
• Prescribed Drugs: Thalidomide, SSRIs, many more!
• Alcohol
• Smoking
• Caffeine
• Low Birth Weight
• Rarely - physical injury, radiation,
Excellent review on Wikipedia : http://en.wikipedia.org/wiki/Teratology
Teratogen Sensitivity Timeline
Mother's Prenatal Influence
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Diet
Age
Prenatal support
Health
Drug use
Alcohol use
– Fetal alcohol syndrome (FAS)
– Fetal alcohol effects (FAE)
• Tobacco use
• Plasticizers & other hormone mimics (Bisphenol A - BPA)
• List of estrogen mimics
Father's Prenatal Influence
• Relatively little research
• Tobacco use
• Drug use
– Cocaine use harmful because tiny specks of cocaine
can bind to sperm and “piggyback” their way into the
zygote
– Marijuana
• Alcohol damages sperm, increases maternal stress
• Treatment of mother
Becoming an Informed Consumer
Optimizing the Prenatal Environment
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Avoid X-rays & birth control pills
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Get rubella vaccination
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Eat well and take prenatal vitamins
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Avoid alcohol and other drugs
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Avoid men who are alcohol or drug users
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Monitor caffeine intake
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Avoid smoking & exposure to secondhand smoke
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Exercise regularly