3. Genetic Foundations
• We carry a “genetic code”
– Inherited from parents
• Fertilized human egg
– Carries human code
• Begin life as a single cell
– Contains our entire genetic code
• (Human egg about to pop)
4. Chromosomes
• Nucleus of each human cell contains
– Chromosomes
• Thread-like structures made up of
deoxyribonucleic acid, or DNA
– DNA
• Complex molecule that has a double helix shape &
contains genetic information
– Unique to all (except identical twins)
» Same genetic code
5. Genes
• Genes
– Units of hereditary information composed of
DNA.
• Short segments of DNA
– Direct cells to reproduce themselves
– Manufacture proteins that maintain life
• Blueprint for cell reproduction
6. Human Genome Project 2003
• Genome
–Complete genetic information (DNA) of an
organism
• Preliminary map of human genome
–Complete set of developmental
instructions for creating proteins that
initiate making of a human organism
• Humans about 30,000 genes
7. Genetic Expression
• Genetic expression affected by their
environmental conditions
– Hormones in blood stream
• Turn genes on/off
– Hormones affected by environmental conditions
such as
• Light
• Day length
• Nutrition
• Behavior
8. Genetic Expression
• Numerous studies show
– External events outside
• Original cell
• Person
• +
– Events inside cell
• Can excite or inhibit gene expression
– Stress
• Hormone: cortisol
– 5 fold increase in DNA damage
» Woman who is pregnant , 4 yr old son missing
9. Genetic Principles
• Dominant-Recessive Genes Principle
– Recessive gene is influential only if both genes
are recessive
– 1 gene of a pair always exerts its effects
examples:
hair color
eyesight
freckles
Genetic Foundations
10. Dominant-Recessive Genes
Principle
• Dominant
– 1 gene of pair always exerts its effects
• Recessive gene
– Exerts influence only if 2 genes of a pair are both
recessive
• may be overridden by dominant gene
• may be carried from generation to generation but not
expressed in phenotype
– Red hair
13. Genetic Principles
• What determines how a genotype is
expressed to create a particular
phenotype?
–Ex: Look exactly like sister/brother?
• Same genetics
–Why not?
–Science not totally sure
15. Genetic Principles
• Sex-Linked Genes: X-linked inheritance
– Mutated gene carried on X chromosome
– Males have only 1 X chromosome
– More vulnerable to X-linked disorders
• Hemophilia
• Fragile-X syndrome
17. Sex-Linked XX or XY
Chromosome Abnormalities
Klinefelter
syndrome
Disorder in males; extra
X chromosome
Fragile X
syndrome
Abnormality in X
chromosome;
becomes constricted or
breaks
Turner
syndrome
Female disorder; X
chromosome
missing or partially deleted
XYY
syndrome
Disorder in males; extra Y
chromosome
Genetic Foundations
19. FROM FERTILIZATION TO EMBRYO
• Here is an interactive site you might find
helpful.
• The Brain From Top to Bottom
• http://thebrain.mcgill.ca/flash/d/d_09/d_09
_cr/d_09_cr_dev/d_09_cr_dev.html
20. 1.V. The Moment of Conception
http://www.youtube.com/watch?v=mdGsLRGBsCU
21. 2. V. Human Development
Human Development
http://www.youtube.com/watch?v=UgT5rUQ9EmQ&feature=PlayList&p=2E2643C1A6F72FBA&index=1
22. Conception & Period of the Zygote
• Zygote
– Egg & a sperm fuse
• Create single cell
– 23 unpaired chromosomes from egg & sperm
combine to form
• 1 set of 23 paired chromosomes
–1 chromosome of each pair is from
• Mother’s egg
• Father’s sperm
–Each parent contributes 1/2 of offspring’s
genetic material
23. Prenatal
Development
• 3 prenatal periods
–1. Germinal Period (period of the zygote)
–2. Embryonic Period
–3. Fetal Period
– (Gabby Eats Frogs)
24. 1.The Germinal Period
• Takes place in 1st 2 weeks after conception.
• 1. Creation of zygote
• 2. Cell division
• 3. Attachment of zygote to uterine
wall
The Course of Prenatal Development
26. • Creation of zygote (fertilized egg)
– Mature human egg
• 23 chromosomes
– Mature human sperm
• 23 chromosomes
– Egg fertilized by sperm
• Creates zygote
• 46 chromosomes
The Germinal Period
27. • Many sperm race to egg
–1 wins…usually.
• Makes way to egg by smell
–Including other mechanisms
• Once a sperm penetrates
–Chemical is released
• Prevents other sperm from entering
The Germinal Period
28. The Germinal Period
• Two sperm fertilize ovum?
–Usually miscarriage
–1% twins (real case)
• 1st twin
–Hermaphrodite
–5% XY, 95% XX
• 2nd twin
–Male, has 50% XX and 50% XY.
32. 2. The Embryonic Period
• Occurs 2 - 8 weeks
– after conception
• Cell differentiation intensifies
• Support systems for cells form
• Organs appear
– Heart first
The Course of Prenatal Development
34. Placenta
• Attaches to inside of uterus
• Connected to fetus by umbilical cord
• Produces pregnancy-related hormones
• Small blood vessels carrying fetal blood run
through placenta, which is full of maternal
blood.
35. Embryo’s Life-Support System
• Placenta
–Intertwines
• Does not join
mother & baby
• Umbilical cord
–Connects baby to
placenta
The Course of Prenatal Development
36. • Amnion & amniotic fluid
–Provides baby’s environment
• Drinks it
• Organogenesis
–Organ formation
–Especially vulnerable to environmental
changes
Embryo’s Life-Support System
37. 3. The Fetal Period
• Begins 2 mo’s after conception
• Lasts @ 7 mo’s - birth
• Largest prenatal size & weight gains
• Development:
– Fingerstoes lungs
– Skin features reflexes
The Course of Prenatal Development
44. The Brain
• Birth – 100 billion neurons
• Basic architecture
• 1st 2 trimesters
– Neural tube: first 18–24 days
• Forms the spinal cord
• Neural Tube Defects
– Effect so severe, won’t show you
– Defect tied to nutrition
The Course of Prenatal Development
47. The Brain
• Neurogenesis:
– 5th prenatal week:
• Proliferation of new immature neurons
• Continues prenatal period
– 3rd trimester
• Connectivity
• Functioning of neurons
48. Fetal Learning
• 3rd Trimester
• Increased responsiveness:
– Familiar voices
• Differences in heart rate
• Experiment
– Cat in the Hat read to fetus
– 2x’s a day
• Preference for book & voice after birth
• Any help to development?
• None detected
52. Threats to prenatal development
• Teratogen
–Any agent that causes a birth defect
• Severity & type of defect affected by
– Dose
– Genetic susceptibility
– Time of exposure
Hazards to Prenatal Development
53. • All drugs (prescribed, illegal) can have
effects on unborn fetus
– Antibiotics, analgesics, asthma medications
– X-rays
– Pollution
– Large doses Vitamin A
– 1961: thalidomide tragedy
Threats to prenatal development
57. Zygote Embryonic period (wks) Fetal Period (wks)
Period of susceptibility
to functional defects
Fig. 3.7 (modified)
1 2 3 4 5 6 7 8 9 16 32 38
Teratogens and Timing of Their Effects
on Prenatal Development
Most
serious
damage
from
teratogens
in first 2–8
weeks
Period of susceptibility
to structural defects
Central nervous system
Heart
Arms
Eyes
Legs
Ears
Teeth
Palate
External genitalia
58. Psychoactive Drugs
• Psychoactive drugs
–Act on nervous system
• Change moods
–Alter states of conscious
• Modify perceptions
–Extent of risk & harm varies
Hazards to Prenatal Development
61. Nicotine (March of Dimes longitudinal study, 2011)
• – Heart defects
– Absence or severe underdevelopment of
hands, feet, radius, tibia, ulna or fibula
– Missing fused or extra fingers or toes
– Clubfoot
– Cleft lip or palate
– Eye defects
– Gastrointestinal defects
• Baby more likely
– 2 or more defects
64. • Weight Gain
– 25 - 35 lbs. best
–Inadequate / excessive
• May affect
– Baby birth weight
– Mother’s health
» Gestational Diabetes
• Lose weight during pregnancy?
– Anorexia / Bulimia
Maternal Nutrition
65. Maternal Nutrition
• Nutrition
–Increased need for all nutrients
–50% increased need for:
• Protein
• Iron
• Vitamin D
• Calcium
• Phosphorus
• Magnesium
–Water essential
Strategies for Expectant Mothers
66. Maternal Nutrition
• Maternal diet, nutrition, & weight
– Folic acid & iron
– Fish: PCBs & mercury levels
• Maternal age
– Highest risks: adolescents, over 35 years
– Down syndrome
• Maternal emotional states
Hazards to Prenatal Development
67. Exercise During Pregnancy
• Decrease duration & intensity as pregnancy
progresses
• Avoid high-risk activities
– Warm up, stretch, cool down
– Reduce exercise significantly in last 4 weeks
• Exercise not linked to preterm birth
Strategies for Expectant Mothers
68. Parental Factors
• Paternal factors
– Father’s diet & low vitamin C
– Drug use effects on sperm
– Smoking – effects of second-hand smoke
– Father’s age at conception
• Birth defects: dwarfism, Marfan’s Syndrome
Hazards to Prenatal Development
