THE START OF LIFE: PRENATAL DEVELOPMENT

CHAPTER 2

STATEMENT OF INTENTFOR 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• Based on discussion w/ my spouse during our trip• Un(der?)-reported Observational Method Error• Author makes this error• People make this error

• 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

Of course, “everybody knows” that observational research is correlational but…

Of course, “everybody knows” that observational research is correlational but…

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

• Genes– Specific DNA sequences

• Chromosomes– Rod-shaped DNA

portions in 23 pairs

– Contain genetic blueprint for individuals

– Replicate through mitosis

# changes fairly regularly

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 chartNote nonlinear scale

Establishing the Sex of the Child

Also XXY and other abnormalities

Mixing and Matching of GenesBasics 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 CodeCracking 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

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

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 DevelopmentHow 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

•Obesity, blood pressure, respiration rates, age at death•Eye color•Hair color•Height•Muscle structure•And so forth

Myths of Human GeneticsRequired reading

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

Genetics and I.Q.Note: IQ is actually far more complex than a single score on a paper test.

Do we inherit our personality?

Genetic and Environmental Influence on Personality: Born to Be Outgoing?

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

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

Older Women and Risks of PregnancyNote dissimilar scales making comparisons confusing

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/TeratologyExcellent review on Wikipedia : http://en.wikipedia.org/wiki/Teratology

Teratogen Sensitivity Timeline

Mother's Prenatal Influence

• 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 ConsumerOptimizing the Prenatal Environment

• Avoid X-rays & birth control pills

• Get rubella vaccination

• Eat well and take prenatal vitamins

• Avoid alcohol and other drugs

• Avoid men who are alcohol or drug users

• Monitor caffeine intake

• Avoid smoking & exposure to secondhand smoke

• Exercise regularly