Prenatal
Development
Sources:
Chromosomes
• Each egg/sperm has 23 chromosomes – these contain the characteristics of each parent
• The first 22 pairs of chromosomes are called autosomes
• The 23rd determines the sex of the child –
When both are X (XX), you have a girl, (XY) is a boy
• DNA (deoxyribonucleic acid) – contains four different chemicals that create the code and building blocks of the body and its formation (adenine, thymine, guanine, cytosine) – all attached on phosphate/sugar spines that wrap around each other
• https://www.youtube.com/watch?v=C Bezq1fFUEA
• Compounds for specific chemical reactions are called Genes
• A complete set of genes = Genotype
• A Phenotype is an individual’s
Your Turn!
•
In your notes….
•
What are alleles and what do they do?
•
Heterozygous vs. Homozygous?
•
Dominant vs. recessive?
•
Issues with different types of alleles?
•
Why might these concepts be needed when
From Conception to Birth –
Zygote (1-2 Weeks)
•
Prenatal Development is the term used to describe the many
changes that occur during the (average) 38 weeks of
pregnancy
From Conception to Birth –
Zygote (1-2 Weeks)
•
After about a week, the zygote implants itself into
the uterine wall and creates blood vessels with the
mother’s body
•
Less than 1mm in diameter
•
Small cells in the centre of the zygote will become
the baby – known as the germ disc
•
What issues could arise during this stage? Impact on
From Conception to Birth –
Embryo (3-8 Weeks)
•
Embryo – a zygote that is completed
embedded in the uterine wall
•
During this period, body structures
and organs develop
•
Ectoderm –nervous system, skin,
and hair
•
Mesoderm – muscles, bones, and
circulatory system
•
Endoderm – digestive system and
lungs
•
Amniotic Fluid cushions the embryo
and maintains temperature –
umbilical cord provides blood,
From Conception to Birth – Fetus
(9-38 Weeks)
•
Fetus grows in weight (30g at 9 weeks, approx. 120g at 4 months, and will
gain 3.4 kilograms in last 5 months)
•
Cartilage turns to bones, and the body’s system finish developing
• Cerebral Cortex grows the most (wrinkled part responsible for regulating
important behaviors
From Conception to Birth - Fetus
•
The Age of Viability – 22-28 weeks – a fetus born
at this age has a chance at survival, however, will
likely face major challenges
•
Fetus can “behave” during this period and
respond to stimuli (reading, music, etc)
Your Turn!
•
Research Question: What affects the development
of a fetus?
•
In what ways?
•
Can these be reversed or changed?
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Does the environment begin to impact the
Risk Factors
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How is prenatal development affected by a Mother’s age,
stress, and nutrition?
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Nutrition – healthy diet is essential
•
E.g. lack of folic acid increases risk of spina bifida (neural tube
doesn’t close properly, resulting in permanent damage to the
spinal cord/nervous system)
•
Poor nourishment could increase the likelihood of premature
birth or the baby being underweight
Risk Factors - Stress
•
Stress – person’s physical/psychological responses to
threating or challenging situations
•
Why stress? Why can’t we “study” stress on pregnant women?
•
Risks include low oxygen, increased heart rate, higher
susceptibility to illness
•
Stressful environments could also lead to poor habits (alcohol,
smoking)
Teratogens
•
Teratogens – harmful agents that cause
abnormal prenatal development
•
Research the Thalidomide Disaster (resulting in 10,
000 babies being born with deformed body parts,
organs)
Teratogens - Drugs
•
Many drugs have common uses, but present dangers
during pregnancy
•
Thalidomide is a teratogen
Drug Potential Consequence
Alcohol Fetal alcohol syndrome, cognitive deficits, heart damage,
delayed growth
Aspirin Deficits in intelligence, attention, and motor skills
Caffeine Lower birth rate, decreased muscle tone
Cocaine + Heroin Delayed growth, irritability in newborns
Marijuana Low birth weight, less motor control, cognitive impairments
Teratogens – Drugs: Alcohol
•
No safe level while pregnant
•
Leading cause of Fetal Alcohol Spectrum
Disorders – developmental disabilities,
learning/attention impairments, hyperactivity,
below-average intelligence, distinctive facial
Teratogens - Diseases
•
Many illness do not affect the fetus, but some can be quite
harmful
•
Medicines can often curb some of the impacts of the disease
Disease Potential Consequences
AIDS Frequent infections, neurological disorders, death
Cytomegalovirus Deafness, blindness, abnormally small head, intellectual
impairment
Genital Herpes Encephalitis (inflammation of the brain), enlarged spleen,
improper blood clotting
Rubella Intellectual impairment, damage to eyes, ears, and heart
Teratogens – Environmental
Hazards
•
We are often exposed to toxins in our industrialized
world – food, air, drink
•
What is a PCB and why is it banned?
•
Liu et. Al. (2003) determined that even low amounts
of air pollution can have adverse effects at birth
Hazard Potential Consequences
Lead Intellectual impairment
Mercury Physical development delay, intellectual impairment,
Cerebral palsy
PCB’s Impaired memory and verbal skill
X-rays Physical development delay, intellectual impairment,
Effects of Teratogens
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1) Impacts of a teratogen depends on the genotype of an organism –
thalidomide tested in rats was normal…)
Effects of Teratogens
•
3) Teratogens affect a specific aspect of prenatal development
– Rubella can cause a baby issues with eyes and ears, but a
mother who eats a PCB-contaminated fish can birth a baby
with a normal body, but with intellectual, motor, and
memory issues
•
4) The impact depends on the dosage - difficult to measure
sensitivity to teratogen – 0 exposure is best
•
5) Symptoms be obvious, or may only show later as the child
develops (PCB-contaminated fish – children seemed normal,
but cognitive functions were delayed later in child’s
Your Turn!
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How can we foster resilience to teratogens?
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What current systems are in place in our society?
•
Are they effective?
•
Where do vaccines fit in?...
•
Research and record ONE genetic disorder. What
chromosome has been linked with the disorder?
•
Is heredity destiny?
•
What developmental theories can aid us in learning
Theories
•
Research the theories of Arnold Gesell and Esther Thelen –
• What concepts do they add to human development?
• In what ways do we use their theories today?
• Now that we know about prenatal development, what do their
concepts add to motor skill development (reaching before printing)?
Suggested Sources
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Gesell
•
http://schoolworkhelper.net/growth-and-development-theory-arnold-gesell-1880-%E2%80%93-1961/
• http://www.gesellinstitute.org/about-us/gesell-theory/
•
Thelen
• https://www.psychologytoday.com/blog/sexing-the-body/201106/in-p
