1. The Cell Cycle, Mitosis, and Cancer
Glencoe Biology Chapter

2. What causes cancer?
Cancer is caused by mutations, which creates abnormal cell growth.
A mutation is a change to an organism’s genetic material. In our case, DNA.

3. What causes mutations? (changes our DNA?)
Radiation
UV radiation
X rays
Chemicals
Alcohol
Tobacco
Drugs
Infectious agents
Viruses like HPV

4. Genetic Material
During most of the cell’s life, genetic material exists in chromatin
Chromatin = DNA that is long and tangled
Chromatin coils up (during M phase) to form chromosomes
When UNCOILED, chromatin can start the process of making proteins and can replicate itself
When COILED, cell division can occur

5. Anatomy of a Chromosome

6. 0.5 µm
Chromosome
duplication
(including DNA
synthesis)
Centromere
Sister
chromatids
Separation
of sister
chromatids
Centromeres
Sister chromatids

7. The Cell Cycle: The “lifetime” of a cell
What do cells spend their lifetime doing?
Cells go through THREE (3) periods
One of growth and synthesis of DNA
One in which the nucleus divides
One in which the cytoplasm divides

8. The Cell Cycle The growth period is called INTERPHASE
The stage during which the cell carries out cellular functions
Also the stage in which it grows and replicates its DNA.
INTERPHASE S
(DNA synthesis) G1
Mitosis G2
Cytokinesis
MITOTIC
(M) PHASE

9. The Cell Cycle The nuclear division period is called M PHASE (Mitosis)
the stage of the cell cycle during which the cell’s nucleus and genetic material divide.
Consists of Prophase, Metaphase, Anaphase, and Telophase (PMAT)
INTERPHASE S
(DNA synthesis) G1
Mitosis G2
Cytokinesis
MITOTIC
(M) PHASE

10. The Cell Cycle The cytoplasmic division period is called CYTOKINESIS
The method by which a cell’s cytoplasm divides, creating a new cell.
INTERPHASE S
(DNA synthesis) G1
Mitosis G2
Cytokinesis
MITOTIC
(M) PHASE

11. So what does this have to do with cancer?
The cell cycle has 3 main checkpoints
If a cell receives a go-ahead signal at the G1 checkpoint, it will continue dividing
If the cell does not receive the go-ahead signal, it will exit the cycle and not divide
Tumors form due to out of control cell division
G1 checkpoint
Control
system S G1 M G2
M checkpoint
G2 checkpoint

12. Mitosis Nucleus Chromatin condensing 10 µm Nucleolus Chromosomes
Cell plate
Prophase. The
chromatin is condensing.
The nucleolus is beginning to disappear.
Although not yet visible in the micrograph, the mitotic spindle is starting to form.
Prometaphase. We
now see discrete chromosomes; each
consists of two identical sister chromatids. Later
in prometaphase, the
nuclear envelope will fragment.
Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at
the metaphase plate.
Anaphase. The
chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore micro-
tubules shorten.
Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.

13. Why do cells need to divide?
In unicellular organisms, division of one cell reproduces the entire organism
Multicellular organisms depend on cell division for:
Development from a fertilized cell
Growth
Repair

14. LE 12-6ca
G2 OF INTERPHASE
PROPHASE
PROMETAPHASE

15. LE 12-6da
10 µm
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS

16. INTERPHASE – BEFORE MITOSIS

17. 1st stage of Mitosis: Prophase
During Prophase…
Chromatin coils up into visible chromosomes
The nucleus will disappear during this phase
Centrioles will begin to separate

18. 2nd Stage of Mitosis: Metaphase
During Metaphase…
Spindle fibers pull the chromosomes to the middle (equator/metaphase plate) of the cell

19. 3rd stage of Mitosis: Anaphase
During Anaphase…
Chromosomes will be pulled apart forming chromatids.
Once the chromatids are separated, they will move towards opposite sides of the cell.

20. 4th stage of Mitosis: Telophase
During Telophase…
The chromatids uncoil, becoming chromatin
The nuclear envelope reforms
Mitosis is COMPLETE!!!

21. Cytokinesis: last stage in the cell cycle
The cytoplasm (and its contents) will divide into two new cells.
ANIMAL CELLS: The cell membrane will move inward and pinch apart
PLANT CELLS: A new cell wall forms between the two new cells.

22. SUMMARY - MITOSIS Number of ROUNDS of cell divisions: 1
Number of daughter cells :
Genetically identical? Yes
Chromosome #: Same as parent
Where: Somatic cells (non-sex cells)
When: Throughout life
Role: Growth and repair

23. The complete CELL CYLCLE
M-PHASE
(mitosis + cytokinesis)
MITOSIS

24. VOCABULARY ! Human chromosome number:
46 in body cells (diploid OR 2N)
23 in sex cells (haploid OR N)
A picture of species’ full set of chromosomes is a KARYOTYPE