1. The Cell Cycle
Essential Standard – Analyze how cells grow and reproduce in terms of interphase, mitosis and cytokinesis

2. Why do cells divide? Cells divide so that….. Cells can remain small
Cells that are too big are not efficient
To replace worn out or damaged cells
For growth in multi-cellular organisms

3. What is the Cell Cycle? The Basics…. The cell cycle is the process by
which a cell grows to its largest
possible size and then divides into
two identical cells.
The parent cell is the cell that
divides.
The daughter cells are the two
resulting cells that are made.

4. Which parts divide?
There are two distinct parts of the cell that must divide: the nucleus and the cytoplasm.
The division of the nucleus is called mitosis.
The division of the cytoplasm is called cytokinesis.

5. What background information do you need first?
When the nucleus divides, it needs to be able to give each daughter cell identical amounts of DNA.
When mitosis begins, the DNA needs to be in a different form than when mitosis is occuring.

6. DNA & How It Is Organized
DNA can be organized in one of two ways:
Chromatin
Occurs this way when the cell is NOT dividing.
Long and stringy
Chromosomes
Occurs this way when the cell is dividing
Dense and compact

7. Chromosome Structure Made of two identical chromatids held
together by a centromere.
Each sister chromatid
has the same genes.

8. Sister Chromatid
Centromere

9. The Cell Cycle The Cell Cycle is made up to 2 parts:
Interphase (Resting Phase)
Mitosis (Dividing Phase)
Occurs in somatic cells (Body Cells)
Does NOT occur in sex cells (egg & sperm)

10. Other Structures Involved…
Centrioles
Found only in animal cells
Location: near the nucleus
Job: to form mitotic spindle; helps to move chromosomes during mitosis.

11. Interphase “Resting” phase (not really, it’s just not dividing!)
Parent cell is busy
Growing & making organelles
Copying chromosomes
Preparing for mitosis!
Similar to “pre-game”

12. More About Interphase Interphase is divided into three parts: G1 phase
S phase
G2 phase

13. G1 Phase
This is also known as Gap 1 phase.
The cells is preparing for DNA synthesis
to occur by making a variety of different
proteins.
The cell will also experience rapid
growth. It will grow to its original size.

14. S phase This is also known as the Synthesis phase.
DNA is replicated during this phase.
At the end of mitosis, each chromosome
only had one sister chromatid. By the end
of the S phase, each chromosome with
have two identical sister chromatids.

15. G2 Phase This is also known as the Gap 2 phase.
The cell is going to make a lot of the proteins
needed to go through mitosis.
The cell also makes more organelles and
synthesizes a great deal of energy.

16. Now we are ready to start mitosis..
Mitosis is division of the nucleus.
It consists of four phases:
Prophase
Metaphase
Anaphase
Telophase

17. Prophase Chromatin turn into chromosomes Nuclear membrane disappears.
Nucleolus disappears.
Centrioles move to opposite ends, the poles.
Mitotic spindle form.

18. Metaphase The shortest phase of the Cell Cycle
Chromosomes line up down the middle of the cell (like stitching on a football)
The centromeres attach to the spindle fibers that run from one centriole to the other.

19. Anaphase Think opposite like an antonym.
Chromatids are pulled to opposite ends of the cell
Cells starts to elongate.

20. Telophase Nuclear membrane reforms. Nucleolus reforms.
Chromosomes change to chromatin.
Cytokinesis begins.

21. Results of Mitosis TWO identical daugther cells
Have the same number of chromosomes!!!