Human development answering questions

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Genetics, Prenatal Development, and Birth

CHAPTER 2

Module 1 – Week 2– Ch. 2: Genetics, Prenatal Development, and Birth

Genes and Chromosomes Blueprints for creating a person are stored  and communicated in our genes, the basic 

units of genetic information

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The Code of Life

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How Are Genes Expressed? Genotype = Genetic Code Phenotype = Gene Expression

Genetic Code Expression

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Determining Sex

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When Development Deviates Inherited and Genetic Disorders

GENETICS SPONTANEOUS  MUTATION

ENVIRONMENTAL INSULT

• Down Syndrome • Fragile X Syndrome • Sickle-cell anemia

Examples include:

• Tay-Sachs disease • Klinefelter's Syndrome

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Dominant Gene Disease

Recessive Gene Disease

Ex: Cystic Fibrosis Ex: Huntington’s Disease

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Environmental Influence

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Gene - Environment Interaction (GXE)

Sandra Scarr suggests three ways that a child's genetic predisposition may influence his or her environment:

PASSIVE EVOCATIVE ACTIVE

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Passive G X E “Genes by Environment” (i.e., interaction between the two)

Biological parents provide environments  (and genes) to their children

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Evocative G X E

Children bring characteristics to environments that evoke certain responses

“Genes by Environment”

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Active G X E

Children seek out certain environments

Ex: “Niche‐Picking” 

“Genes by Environment”

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Review and Apply

APPLYAPPLY

• How might an environment different from the one you have experienced in your lifetime affect your development? Would your personality, behavior or accomplishments look any different?

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Prenatal Growth and Birth

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Stages of Prenatal Development Germinal Stage: Fertilization ‐2  Weeks

Embryonic Stage:  2‐8 Weeks

Fetal Stage: 8 weeks ‐ Birth

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Fertilization

Gametes from male and female join (sperm and ovum)

Zygote created from fused gametes

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More than one?

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Multiple births have increased over

the last 25 years. Why?

• Fertility Drugs • Mother’s Age • Diverse Population

SOURCE: National Vital Statistics Reports, “Births: Final data for 2013”

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Germinal Stage Fertilization  two weeks

Shortest stage

Fertilized egg now called blastocyst

Travels to and implants in uterus

Characterized by methodical cell division ◦ Cell specialization

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Embryonic Stage 2 weeks  8 weeks

Organism firmly secures to uterus and called an embryo

Organogenesis ◦Development of major organs and basic anatomy

Three distinct layers that ultimately form different set of structures:

◦Endoderm

◦Mesoderm

◦Ectoderm

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Fetal Stage 8 weeks  Birth

Organism now called fetus

Characterized by rapid development

Formally starts when differentiation of major organs has occurred

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Body Proportions

At two months,  head represents  about half the  fetus, but by the  time of birth, it is  one‐quarter of  its total size

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Infertility, Miscarriage and Abortion

Occurrence Prevalence Causes / Outcomes

INFERTILITY 15% 

of couples

Maternal: age, hormones, stress, drug use Paternal: drug use, tobacco, STI (STD) Outcomes: anxiety / depression, grief

MISCARRIAGE 15 – 20%

of pregnancies

Causes: often genetic abnormality, drug use,  incompatible blood, Rx drugs (historically) 

Outcomes: grief, depression, difficulty caring for  future children

ABORTION Outcomes: Mix of relief / regret, short‐term 

mental distress / disorder

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Threats to Development

Teratogen: Environmental agent  that causes damage  during prenatal 

period.

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Teratogens

Prescription & Non-prescription Drugs

Psychoactive Drugs

Environmental Hazards

Infectious Diseases

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Critical Periods

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Mother's Prenatal Influence

 Diet

 Age

 Prenatal support

 Prescriptions

 Health

 Drug use

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Father's Prenatal Influence

Relatively little research

Tobacco use

Drug use

Alcohol use

Treatment of mother

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Optimizing the Prenatal Environment

Avoid X‐rays and birth control pills; get rubella  vaccination

Eat well and take prenatal vitamins

Avoid alcohol use and other drugs

Monitor caffeine intake.

Avoid smoking and exposure to secondhand  smoke

Exercise regularly

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Fetal Development Monitoring Techniques

Technique Description

Amniocentesis • Fifteenth and twentieth week of pregnancy • A sample of the amniotic fluid

Chorionic villus  sampling (CVS)

• Done at 8 to 11 weeks • either transabdominally or transcervically, depending on 

where the placenta is located. Involves inserting a  needle (abdominally) or a catheter (cervically) into the  placenta but staying outside the amniotic sac 

• This tissue is manually cleaned of maternal uterine  tissue and cultured

Ultrasound  sonography

• Uses very high frequency sound waves to detect  structural abnormalities or multiple pregnancies,  measure fetal growth, judge gestational age

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Stages of Labor Stage 1 Stage 2 Stage 3

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Birth Complications Problem Description Outcomes Treatments

Preterm Prior to 38  weeks

Health and developmental  problems, lower academic  achievement, breathing  problems, ADD / ADHD, 

newborn death

Massage,  Kangaroo Care 

Low  Birth‐weight

Less than 5.5  pounds

7% of all US  births

Small for  Gestational  Age (SGA)

Below 10th

percentile  for that age

Malpresentation

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Very low birth‐weight infants Most vulnerable; immaturity of their organ systems

Weigh less than 1250 grams (around 2 1/4 pounds)

Normal, 2 day old  baby (8.2 lbs.)

4 weeks old, born at 30  weeks (~2 mos. early)

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Post-mature Babies: 2 weeks + overdue

 Blood supply from placenta may become insufficient

 Blood supply to brain may be decreased, leading to the potential of brain damage

 Labor becomes riskier for larger fetus to pass through birth canal

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