The Developing Person
Through the Life Span 8e
by Kathleen Stassen Berger
Chapter 3 Heredity & Environment
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The Genetic Code
Epigenetics
Gene-Gene Interactions
Chromosomal & Genetic Problems
The Genetic Code
Gene
Small section of a chromosome, the basic unit for
transmission of heredity.
Consists of a string of chemicals that provide
instructions for the
cell to manufacture
certain proteins
The Genetic Code
Chromosomes:
 Molecules of DNA
 DNA consists of 46
chromosomes
arranged in 23 pairs
Genome:
 The full set of genes that are
the instructions to make an
individual member of a
specific species
The Beginnings of Life
Gametes
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Reproductive cells (sperm and ova)
Each consists of 23 chromosomes.
Zygote
Two gametes (sperm and ovum)
combine and produce a new
individual with 23 chromosomes
from each parent.
Genotype vs Phenotype
Genes are passed down
from generation to
generation
Genotype
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An organism’s genetic
inheritance, or genetic potential
Unique for each organism
Phenotype
Observable characteristics,
including appearance, personality,
intelligence, and all other traits.
The Beginnings of Life
 The zygote begins duplication and division then
differentiation and specialization occur.
 Cells change from being stem cells, those from
which any other specialized type of cell can form, to
being only one kind of cell.
Twins
Monozygotic (identical) twins
 Originate from one zygote that
splits very early in development
 Same genotype
Dizygotic (fraternal) twins
 Result from fertilization of two
separate ova
 by two separate sperm
 Incidence is genetic and varies by
ethnicity and age
The Developing Person
Through the Life Span 8e
by Kathleen Stassen Berger
Chapter 4 –
Prenatal Development and
Birth
Prenatal Growth
Three main periods of prenatal development
1. Germinal Period (1st two weeks after conception):
rapid cell division and beginning of cell differentiation
2. Embryonic Period (3rd through 8th week): basic
forms of all body structures develop
3. Fetal Period (9th week until birth): fetus grows in
size and matures in functioning
The Germinal Period
 Zygote begins duplication and division within hours
of conception
 Development of the placenta
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Organ that surrounds the developing embryo
Sustains life via the umbilical chord
 Implantation (about 10 days after conception)
 Developing organism burrows into the placenta that lines the
uterus
The Embryonic Period
Embryo
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3rd through the 8th week after conception
Begins when the primitive streak appears down the middle
of the cell mass
Primitive streak becomes the neural tube and later the
brain and spinal column
Eyes, ears, nose, and mouth form
Heart begins to pulsate
Extremities develop and webbed fingers and toes separate
The Fetal Period
Fetus
9th week after conception until birth
Growth period
Heartbeat detectable via stethoscope
Cortex is not fully mature at birth
Brain at birth is biggest part of baby
Age of Viability
Age of Viability
 Age at which a preterm
newborn may survive
outside the womb with
medical care
 About 22 weeks after
conception
 Brain is able to regulate
basic body functions
 Chances of survival increase
with each day after the 22week mark
Who is likely to have a preterm
birth?
 Best predictor is a previous preterm
delivery
 Family History
 Multiple Births (twins or more)
 Women with uterine or cervical
abnormalities
Preterm Births
Medical Factors Increasing the Likelihood of a
Preterm Birth
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Diabetes
High Blood Pressure
Clotting Disorders
Birth defects in baby
Mother overweight/very underweight
Short time between pregnancies
Preterm Births
Lifestyle Factors Increasing the Likelihood of a
Preterm Birth
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Lack of Social Support
Late/No Prenatal Care
Domestic Violence
Smoking During Pregnancy
Drinking Alcohol/Drugs
Stress
Research suggest low socioeconomic status and lower
education level are significantly related to preterm
births
Low Birthweight
Low Birthweight (LBW)
less than 5 ½ lbs.
Very Low birthweight (VLB)
less than 3 lbs 5 ounces
Extremely Low Birthweight (ELB)
less than 2 lbs 3 ounces
Consequences of Low Birthweight:
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Cognitive Difficulties
Delayed pre-linguistic and linguistic development
Visual and hearing impairments
Attention Difficulties
Behavioral Difficulties
Higher rates of obesity, heart disease, and diabetes
Birth
Apgar scale
Quick assessment of newborn’s heart rate, breathing,
muscle tone, color, and reflexes
 Completed twice (1 minute and 5 minutes after birth)
 Score of 0, 1, or 2 in each category
 Desired score: 7 (total) or above
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Harmful Substances
 Teratogens
 Substances and conditions that can impair prenatal
development and result in birth defects or even death
 Behavioral Teratogens
 Affect the child’s developing brain
 Developmental
disabilities
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retardation, hyperactivity, and learning
Effects do not become evident for months or years
Birth Defects from Teratogens
Applying the Research
 Fetal alcohol
syndrome (FAS)
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A cluster of birth defects
including abnormal
facial characteristics,
slow physical growth,
and retarded mental
development
May occur in the child of
a woman who drinks
alcohol while pregnant
Moving and Perceiving
The first movements are not skills but reflexes,
involuntary responses to a particular stimulus.
 Brazelton Neonatal Behavioral Assessment
Scale (NBAS)
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A test that measures responsiveness
Records 46 behaviors, including 20 reflexes
Infant Reflexes
Reflexes aid survival
breathing, thrashing, sucking, rooting, swallowing, spitting up
Reflexes Signal Normal Functioning
Babinski reflex
When feet are stroked, their toes fan upward.
Stepping reflex
When held upright with feet touching a flat
surface, infants move their legs as if to walk.
Swimming reflex
When laid horizontally on their stomachs,
infants stretch out their arms and legs.
Palmar grasping reflex
When something touches infants’ palms,
they grip it tightly.
Moro reflex
When someone startles them, infants fling their arms
outward and then bring them together on their chests,
as if to hold onto something, while crying with wideopen eyes.