1. Chromosomes & Cell Division
Objectives:
D2 – Identify the parts of a chromosome
D3 - Describe the stages of the cell cycle including DNA replication, mitosis, and the importance of the cell cycle to the growth & repair of organisms
D4 - Recognize that disruptions of the cell cycle can lead to cancer

2. Chromosome
- Super-coiled DNA

3. Chromosome Parts Chromatid - one half of a replicated chromosome
Centromere – protein disk that plays a role in chromosome movement; where the spindle fibers attach

4. Cell Division - the process by which a cell divides
There are 2 types of cell division:
Mitosis – for growth & repair [now]
Meiosis – for making sex cells (gametes) [later]
Mitosis

5. Cell Cycle - the series of events that cells go through as they grow and divide
Grows more in preparation for mitosis
Mitosis (PMAT) & Cytokinesis
DNA Replication
Resting
Growth

6. Cell Growth (G1 & G2 phases) “G” stands for growth
The larger a cell becomes, the more demands the cell places on its DNA.
The cell also has trouble moving nutrients and wastes across the cell membrane.
Small cells function more efficiently than large cells.
Notice that the size of the nucleus doesn’t change.

7. DNA Replication (S phase) “S” stands for synthesis
- Copying process by which a cell duplicates its DNA
DNA – Genetic Information
DNA – Deoxyribonucleic acid

8. Mitosis (during M phase)
- consists of 4 phases
Prophase
Metaphase
Anaphase
Telophase

9. Cytokinesis (during M phase)
- Animal cells
The cell membrane is drawn inward forming a cleavage furrow until the cytoplasm is pinched into 2 nearly equal parts
- Plant cells
A cell plate gradually develops into a separating membrane.

10. Cell Cycle Regulators
Cyclin
a protein that regulates the timing of the cell cycle
- Cancer
Uncontrolled cell division of abnormal cells
Cells do not enter the Go (resting) phase

13. Mitosis for growth & repair
Chromosome
Mitosis for growth & repair
Centrioles
Spindle fibers

14. What cells actually look like during cell division
This is part of an onion plant magnified about 40 times so you can see individual cells.

15. Etymology
Mitosis: mitos- (Gk. warp thread) + -osis (L. act, process). So called because chromatin of the cell nucleus appears as long threads in the first stages.

16. Practice Chromatid Centromere 1 – 2 –
Name the parts of the chromosome:
1 –
2 –
Chromatid
3 – short arm
4 – long arm
Centromere