1. Cell Differentiation:
cells are genetically programmed to be
specialized and will assume unique structural
& functional attributes
Fertilized Egg = totipotential stem cells
vs.
pleuripotential stem cells

3. Oocyte with sperm = fertilization
Zygote=fertilized egg

4. Series of mitotic divisions = cleavage
2-cell stage (30 hours post fertilization)

5. Zygote
2-Cell
Morula Cells

6. 8-Cell Stage…
                                 

7. Morula= solid ball of cells (32 cells +)

8. Blastocyst=hollow ball of cells, implants in
uterus 6-7 days after fertilization
( cells)
Trophoblast=
Chorion
placenta
Inner cell mass=
embryo +
amniotic sac

9. Embryonic disk develops from inner cell mass
gastrulation= endoderm
Somites mesoderm
ectoderm
(2nd week) = embryonic stage

10. Endoderm (inner layer)=
-respiratory system
-Pharnyx (throat)
-Pancreas
-Liver
-GI tract
Mesoderm (middle)=
-gonads
-kidneys
-circulatory system
-Somites = muscles, skeleton

11. Ectoderm (outer layer)=
-skin
-hair
-inner ear
-lens of eye
-nervous system
-connective tissues

12. Neurulation= nervous system forms
(3rd week)
(2mm long)

13. Spina Bifida

14. Anencephaly

15. Extraembryonic Membranes
Trophoblast= placenta + chorion
Inner cell mass= embryo +
amniotic sac +
allantois (bladder & umbilicus) +
yolk sac (nutrients & germ cells)

16. 4th week= Organogenesis
-heart begins to beat (70 bpm)
[2.5 billion beats per 70 years]
-5 mm long
-susceptible to teratogens
[thalidomide]

17. 2nd Month = Morphogenesis
-arms, legs, tail bone form
-25 mm long
-major organs continue to form
6 week embryo

18. 7th week= sexual differentiation occurs
                                         

19. 8th week embryo becomes a “fetus”

20. -most major organs are formed -placenta takes over pregnancy
End of 1st trimester
-most major organs are formed
-placenta takes over pregnancy
2nd trimester (175 mm; 225 gm)
-organs grow
-nervous system continues
development
3rd trimester
-baby grows rapidly!
-6th month=1.3 lbs; 1 ft long
                            

21. What controls growth & development? GENES!
                                        

22. Hutchinson-Gilford Syndrome (Progeria)
8 year old child with
Hutchinson-Gilford Syndrome
(Progeria)
                               

23. Homeotic Genes (Hox)= act as switches and control pattern formation
during development
Dermatomes

24. Mutations: changes made in normal genetic sequence of DNA
A. Cells have DNA repair mechanisms
but… ~ 1 out of 1 billion mutations aren’t repaired
B. If change affects last nucleotide of codon = okay
if 1st codon affected = bad
Why?
[Overhead]
C. Mutagens: agents which cause mutations
(e.g., radiation… UV-B, X-rays, sodium nitrite,
cigarettes

25. Mutations
Point mutations: one nitrogen base gets substituted for another.
Ex. DNA normally read as….
…GGTCTTCTC…
UV radiation zaps and changes message to….
…GGTCATCTC
The result is Valine gets substituted for Glutamine… causing the disease….

26. Sickle Cell Anemia

27. Sickle Cell Anemia:

28. e.g. Sickle Cell Anemia HbA HbS HbA/HbA HbA/HbS HbS/HbS
¼ normal; ½ sickle cell trait;
¼ sickle cell anemia

29. Sickle Cell Anemia and Malaria

30. Malaria & Sickle Cell Allele Distribution

32. Mutations
b. Frame-shift: an extra nucleotide gets slipped into message…
THE CAT RAN FAR…..
THE QCA TRA NFA R
c. Insertions: extra messages added
THE FAT CAT RAN FAR
d. Deletions: messages removed
THE RAN FAR

33. A Deletion Mutation…

34. Mutations:
e. Trisomy: extra chromosomes are added
to our “Karyotype” = usually
lethal

35. Trisomy 21 and Down’s Syndrome