1. How does an embryo develop?

2. How does the zygote form?
Zygote – A fertilized egg

3. What happens to the zygote after it is formed?
Mitosis – causes the zygote to repeatedly divide producing the developing embryo.

4. Embryonic Development:
Fertilization
Mitosis +
Sperm
Egg
Zygote
Embryo- the stage in human development from the
first division of the zygote until about nine weeks
after fertilization.

5. Cleavage
The term used to describe the early cell division associated with embryonic development.
During this time period, the number of cells increase tremendously.

6. The result of cleavage is an embryo that is …..
Morula
A solid ball of cells which moves towards the uterus

7. Mitosis continues & the embryo becomes……
Blastocyst
A hollow ball of cells

8. Cell division continues & the embryo starts to ….
Gastrula
Fold inwardly

9. Gastrulation Three layers
Each layer will eventually form the different organ systems

10. CELLULAR DIFFERENTIATION
Due to gene expression, cells undergo cellular differentiation, in which the cells become increasingly specialized in structure & function.

11. Gene Expression Genes that are being expressed are “on”
Though all genes of the genome are present in every
type of cell, only a small, specific fraction of these
genes are actually expressed in each type of cell.

12. What makes some cells turn “on” some genes while other genes are “off”?
Environmental influences from within the cell, from
surrounding cells, or from outside the organism.

13. These seeds carry the same genes for chlorophyll: CC
Why are they different?
These seeds carry the same genes for chlorophyll: CC
Grown in dark
Grown in light
ENVIRONMENT AFFECTS
GENE EXPRESSION

14. Differentiation’s ultimate goal
An embryo with many different types of cells

15. Stem Cells
Stem cells are embryonic cells that can turn into any type of cell in the body

16. How can stem cells help us?
Can be used to make any type of cell that needs to be replaced in our bodies

17. Why is the use of stem cells so controversial?
They are often taken from fetuses.
Opponents believe that you are killing a life.

18. Are stem cells only embryonic?
No, there are some adult stem cells, but they don’t have the potential to become any kind of cell

19. A Cell Stem Story
Award-winning 15 minute video introduction to stem cell research