1. Interphase and Mitosis
The Cell Cycle
Interphase and Mitosis

2. All living things.. ..begin life as a single fertilized cell.
Humans begin as a fertilized OVUM or human egg cell.

3. The egg cell …
….then begins to divide into exact duplicate “stem cells”.
these first cells will be the basis for all future cells in the human body.
---->note the ovum has divided into 8 stem cells

4. This little batch of cells…
…will not stay the same. Cells specialize and take on different jobs.
>at 5-6 weeks the embyro has animal-like features including a fully functional heart.

5. When Cells Divide Type of Cells How Often Cells Divide Embryo Cells
30 minutes
Intestinal Cells
3 days
Blood Cells
3 months
Nerve Cells
Never / Very Rare

6. Nerve cells… …remain in INTERPHASE for long periods of time.
They go through mitosis about once every 75 years.

7. Cancer cells… …behave much differently than nerve cells.
…spend very little time in interphase and go through mitosis uncontrollably.
Approx. 1/10,000 of your cells are cancerous-the good news-your defense cells usually kill them fast

8. How does this work? Let’s go back to the little batch of 8…
We will now look at cells when they are dividing…and when they aren’t!

9. Interphase The time between cell division Cell is doing its job
Genetic material is all strung out as chromatin – can’t see chromosomes
The time between cell division
Cell is doing its job
DNA duplicates-chromosomes make exact copies of themselves
Nuclear membrane
clearly in place

10. Mitosis (division of the nucleus) There are four different stages
Prophase
Metaphase
Anaphase
Telophase

11. Prophase
DNA condenses to form distinct DOUBLE chromosomes (2 copies of each)
Nuclear membrane disappears

12. Metaphase
Copied chromosomes line up in the middle (equator) of the cell
Spindle fibers attach to chromosomes

13. Anaphase
Copies of chromosomes separate and move toward opposite ends of the cell (poles)

14. Telophase Single chromosomes reach the poles
New nuclear membrane forms around each set
Chromosomes unwind to become thread-like chromatin again

15. Cytokinesis (End of Telophase)
The cytoplasm is evenly divided
New cell membrane forms in animal cells
New cell wall is built across for plant cells