1. Cell Division and Mitosis
Ch. 10

2. Limits to Cell Growth Problems with large cells: Solution:
DNA Overload –
Too much work, not enough DNA to do it!
Exchanging Materials
Moving nutrients and wastes is more difficult if cell is too large
Solution:
Divide!
Cell Division: The process by which a cell divides into two new daughter cells

3. Cell Cycle
Cell Cycle: series of events that cells go through as they grow and divide
During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells, each of which begins the cycle again.

4. Cell Cycle 4 Phases ***G1, S, and G2 all make up Interphase
G1 phase – Cell Growth
S phase – DNA replication – chromosomes are replicated
G2 phase – organelles are replicated
M Phase – Cell actually divides
Mitosis – 4 steps
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis – division of the cytoplasm
***G1, S, and G2 all make up Interphase

5. The Phases of Mitosis 1. Prophase Chromatin condenses into chromosomes
Chromatin is a tangled mass of DNA
Centrioles separate
Spindle begins to form
Nuclear envelope breaks down

6. The Phases of Mitosis 2. Metaphase
Chromosomes line up across center of cell at metaphase plate
Spindle fibers attach to chromosomes at centromeres

7. The Phases of Mitosis 3. Anaphase
Spindle fibers pull sister chromatids to opposite poles
Sister chromatids are separated into individuals chromosomes

8. The Phases of Mitosis 4. Telophase
Chromosomes gather at opposite ends of the cell
Nuclear envelopes reform

9. Cytokinesis Cytokinesis = division of the cytoplasm
Each daughter cell has an identical set of chromosomes

10. Controls on Cell Division
If there is open space between cells, then the cells will divide
If there is no space, cell division will not take place
Cell division occurs to replace dead or nonworking cells, as well as help tissues heal if damaged (i.e. cut in your skin)

11. Cell Cycle Regulators Cyclin – protein used to regulate the cell cycle
Many other proteins also play a role in regulation
Internal regulators: proteins that regulate cell cycle within the cell
Makes sure the cell proceeds to the next phase of they cell cycle only when the previous stage is completed
External regulators: proteins that regulate cell cycle from the outside
Controls the rate of cell division
Can tell a cell to stop dividing if neighboring cells are getting to close

12. Uncontrolled Cell Growth
When cells divide uncontrollably, there can be severe consequences
Cancer: a disorder where cell growth and division is uncontrolled
Cancer cells fail to respond to cell cycle regulators
Cancer cells reproduce constantly resulting in tumors (masses of cells)
Caused by a variety of things:
Smoking
Radiation
UV light (skin cancer)
Certain medications (increase the risk)