1. The Cell Cycle
Biology
Fall 2016

2. Think About It…..
When a living thing grows, what happens to its cells?
What is there about growth that requires cells to divide and reproduce themselves?

3. Information “Overload”
Living cells store critical information in DNA.
As a cell grows, that information is used to build the molecules needed for cell growth.
As size increases, the demands on that information grow as well. If a cell were to grow without limit, an “information crisis” would occur.

4. Information “Overload”
Compare a cell to a growing town. The town library has a limited number of books. As the town grows, these limited number of books are in greater demand, which limits access.
A growing cell makes greater demands on its genetic “library.” If the cell gets too big, the DNA would not be able to serve the needs of the growing cell.

5. Traffic Problems
As the town grows, more and more traffic clogs the main street. It becomes difficult to get information across town and goods in and out.
A cell that continues to grow would experience “traffic” problems.
If the cell got too large, it would be more difficult to get oxygen and nutrients in and waste out.

6. The Prokaryotic Cell Cycle
Binary fission is a form of asexual reproduction
Two genetically identical cells are produced
For example, bacteria reproduce by binary fission.

7. The Cell Cycle
At this moment, millions of cells in the body are dividing, which is part of the process in the cell cycle.
Cell Cycle- the regular sequence of growth and division that cells undergo which is divided into three main stages:
Interphase
Mitosis
Cytokinesis

8. Stage 1: Interphase
This is the time period before cell division where:
The cell grows
Makes a copy of its DNA
Prepares to divide into two cells

9. The Eukaryotic Cell Cycle
The eukaryotic cell cycle consists of four phases: G1 S G2 M.

10. The Eukaryotic Cell Cycle
Interphase is the time between cell divisions.
It is a period of growth that consists of the G1, S, and G2 phases.
The M phase is the period of cell division.

11. Stage 2: Mitosis
The stage during which the cell’s nucleus divides into two new nuclei- one copy of the DNA is distributed into each of the two daughter cells.
Mitosis is divided into four phases:
Prophase
Metaphase
Anaphase
Telophase

12. Stage 3: Cytokinesis This is the final stage The cytoplasm divides
The organelles are distributed into each of the two new cells.
Usually begins during Telophase of mitosis

13. Cytokinesis in Animal Cells
The cell membrane is drawn in until the cytoplasm is pinched into two equal parts.
Each part contains its own nucleus and organelles.

14. Cytokinesis in Plant Cells
In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall.
Instead, a cell plate forms between the divided nuclei that develops into cell membranes.
A cell wall then forms in between the two new membranes.