1. Cell Division: Mitosis
Chapter 8

2. Prokaryotic Cell Division
Binary fission: dividing in half
Steps
Chromosomes duplicate and move to ends of cell
Cell elongates
Plasma membrane pinches off into 2 ‘daughter cells’

3. Chromosomes 1 chromosome is 1 DNA molecule w/ 100’s to 1000’s of genes
Composed of chromatin
DNA and protein
Number varies within species
46 in humans
78 in dogs
38 in cats
254 in shrimp
1200 Adders-tongue (fern)

4. Eukaryotic Cell Division
Chromosomes replicated to form 2 sister chromatids
Joined by centromere
Division splits chromosome apart
Each becomes a chromosome
Count centromeres to determine number

5. The Eukaryotic Cell Cycle (Overview)
Interphase
About 90% of time
Chromosomes not visible yet
3 Subphases
G1 phase = cell growth and maturation
S phase = synthesis, chromosomes replicated
G2 phase = growth and prep for division
G0 phase = not dividing or quienescent
Mitotic (M Phase)
Actual cell division
Mitosis – nuclear division
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis – cytoplasmic division
Repeat
Mitotic Phase

6. Prophase Events Sister chromatids condense
Nuclear envelope begins to disappear
Centrosomes (centrioles in animal cells) move to opposite ends of cell
Mitotic spindles form

7. Metaphase Events Centrosomes at opposite ends of cells
Sister chromatids line up with centromere on metaphase plate
Microtubules attached to each chromatid at the centromere

8. Anaphase Events Sister chromatids separate
Single chromosomes move toward opposite ends of the cell
Microtubule ‘tug of war’
Cell elongates

9. Telophase Events Daughter nuclei form Nuclear envelope reforms
Chromosomes begin to uncoil
Mitosis is complete

10. Cytokinesis Division of cytoplasm Animal cells Plant cells
Begins at the end of telophase (late anaphase too)
Animal cells
Cleavage furrow forms
Microfilaments interact to pinch plasma membrane in 2
Plant cells
Cell plate forms
Vesicles collect in the middle until fuse with plasma membrane

11. Apoptosis Programmed cell death Necessary for normal development
Maintains balance of cell growth
Organism shape/form development
Sunburn peeling
Tightly regulated to maintain balance

12. Cell Division Control
Cyclical control system regulates with ‘checkpoints’
3 major ones: G1, G2, and M
Ensures previous processes complete before allowing continuation of division
Possible number of divisions varies
Ends of chromosomes dictate
Skin cells and those of GI tract divide regularly
Liver cells rarely divide
Need growth factors, proteins secreted by the body to stimulate growth
Cells respond to specific ones
Density-dependent inhibition
Cells stop dividing if become crowded
Remove cells and dividing restarts
Anchorage dependence
Must have contact w/ a solid surface

13. Cancer Cancer is a disease of the cell cycle
Only 1 cell needs to be transformed into a cancer cell
Immune system normally detects then destroys
Undetected can proliferate = tumor
Benign stay in original location
Can be removed by surgery so don’t disrupt organs
Malignant can spread into other areas
Metastasis: cancer cells spread via the circulatory system from original site
Don’t follow normal signaling
No density-dependent inhibition (overlap)
No check points
Make own growth factors to increase proliferation
Unlimited number of divisions
Often named for site of origin
4 categories

14. Cancerous Cell Growth

15. Categories of Cancer Carcinomas Leukemias and lymphomas Sarcomas
External or internal coverings of the body
E.g. skin or intestinal linings
Leukemias and lymphomas
Blood forming tissues
E.g. bone marrow or lymph bodies
Sarcomas
Tissues that support the body
Eg. Bones or muscle

16. Cancer Treatments Radiation for localized cells
Damages DNA of cancer cells more than normal ones
Lost ability to repair
Chemotherapy for metastatic tumors
Drugs interfere with cell division (normal and abnormal) and cause side effects
Nausea from intestinal cells
Hair loss from hair follicle cells
Infections from immune system cells