1. PART 3 Honors Genetics Ms. Day
Mitosis and Cancer
PART 3
Honors Genetics
Ms. Day

2. Another Type of Cell Division: Binary Fission
Prokaryotes (bacteria)
Reproduce by a type of cell division called binary fission

3. The bacterial chromosome replicates
In binary fission,
The bacterial chromosome replicates
The two daughter chromosomes move apart
Origin of
replication
E. coli cell
Bacterial
Chromosome
Cell wall
Plasma
Membrane
Two copies
of origin
Origin
Chromosome replication begins.
Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell. 1
Replication continues. One copy of the origin is now at each end of the cell. 2
Replication finishes. The plasma membrane grows inward, and
new cell wall is deposited. 3
Figure 12.11
Two daughter cells result. 4

4. The cell cycle is HIGHLY regulated
The frequency of cell division
Varies with the type of cell
These cell cycle differences
Result from regulation at the molecular level

5. Cell Cycle Checkpoints
The clock has specific checkpoints
a critical control point
stop and “go-ahead” signals  regulate cycle
signals report whether crucial cellular processes up to that specific point have been completed and completed correctly
There are 3 checkpoints
G1 checkpoint
G2 Checkpoint
M checkpoint

6. The Cell Cycle Control System
Figure 12.14
Control system
G2 checkpoint
M checkpoint
G1 checkpoint G1 S G2 M

7. G1 Checkpoint
G1 checkpoint G1 G0
If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in cell cycle.
If a cell does not receive a go-ahead signal at the G1checkpoint, cell exits the cell cycle and goes into G0, a nondividing state.
Figure A, B

8. G1 Checkpoint Right before S phase
Checks cell size & original DNA for damage
Makes key decisions  will cell divide or enter G0 (resting) phase
Some cells enter a resting state (G0) permanently

9. G2 Checkpoint Checks cell size
Checks for DNA damage/mutations (from replication)
Occurs at END of G2  starts M phase

10. M Checkpoint
Makes sure spindle is correctly attached to EACH chromosome
Makes sure all chromosomes are aligned correctly at the mitotic plate
In a single file line!

11. Chromosomes are lined up in middle of cell

12. The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinases
Two types of regulatory proteins in cytoplasm are involved in cell cycle control
Cyclins
Cyclin-dependent kinases (Cdks)

13. CYCLIN DEPENDENT KINASE (CDK)
INACTIVE FORM
CYCLIN DEPENDENT KINASE (CDK)
CYCLIN +
ACTIVE FORM
CDK/CYCLIN COMPLEX

14. Active vs. Inactive??
What happens when cyclins and cdks are in the ACTIVE form?
Cells can pass through the cell cycle to the NEXT phase 
What happens when cyclins and cdks are in the INACTIVE form?
Cells can NOT pass through the cell cycle to the NEXT phase 

15. cyclin degrades & breaks apart cyclin degrades & breaks apart
“OFF”  RED LIGHT
cyclin degrades & breaks apart

16. What degrades (breaks down) cyclins?
Proteolytic enzymes (proteins)
Break down/degrade cyclins  cause them to fluctuate in [ ]
“PROTEO” means protein
“LYTIC” means break or lyse
REMEMBER:
Cyclin concentration fluctuates (changes)
Cdk concentration stays the SAME

17. Different Cyclins and CDKs for each checkpoint
Cyclin D-CDK4
Cyclin E-CDK2
Cyclin A-CDK2
Cyclin B-CDC2

18. Control of Cell Cycle Animations
Amination #8

19. Programmed Cell Death (Apoptosis)
If cell does NOT pass checkpoints it might need to be killed!
Cell signaling is involved in programmed cell death needed to maintain healthy tissues/ cell function
2 µm
Figure 21.17

20. What CONTROLS the Checkpoints?
Both internal (inside the cell) and external (outside the cell) signals

21. Internal and External Signals
Internal signals
DNA replication
Growth/Nutrition
CDK/Cyclins
External signals
Growth factors & Hormones
Density Dependent Inhibition
Anchorage Dependence

22. External Influences on Cell Division
Growth factors & hormones
Stimulate other cells to divide
Density-dependent inhibition
Crowded cells stop dividing
Most animal cells exhibit anchorage dependence
Cells must be attached to a structure to divide
Ex: extracellular matrix of a tissue other protein or cells

23. Normal mammalian cells.
Cells anchor to dish surface and
divide (anchorage dependence).
When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).
If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition).
Normal mammalian cells.
**The availability of nutrients, growth factors, and a substratum for attachment limits cell density to a single layer.
(a)
25 µm
Figure A

24. Cancer cells
Exhibit neither density-dependent inhibition nor anchorage dependence
Immortal cells (if enough nutrients)
25 µm
Cancer cells usually continue to divide well
beyond a single layer,
forming a clump of overlapping cells.
Figure B

25. Loss of Cell Cycle Controls in Cancer Cells
Do not “listen” to control mechanisms (internal and/or external)
CONTINUE TO DIVIDE
Form tumors
TUMOR= mass or group of abnormal dividing cells

26. Why are Cancer cells IMMORTAL?
Don’t need growth factors  maybe they make their own growth factors
Mutations in GENES!!!
Ex: cyclin or Cdk genes
CANCER IS CAUSED BY A LOT OF MUTATIONS (AN ACCUMULATION OF MUTATIONS)

27. Loss of Cell Cycle Controls in Cancer Cells
Normal cell  cancer cells using process of transformation
Form tumors
Benign  “fine”
Clump of cells remain at orginal spot
Malignant  “mean” “cancer”
Loose/destroy attachments to other cells  they can spread!!!

28. Malignant tumors
These tumors invade surrounding tissues and can metastasize
Tumors that can SPREAD and form secondary tumors
USE BLOOD STREAM and LYMPH VESSELS TO SPREAD!!!

29. Pre-cancerous group of cells = polyp
Tumor
Glandular
tissue
Cancer cell
Blood vessel
Lymph vessel
Metastatic Tumor
Cancer cells invade neighboring tissue. 2
Cancer cells spread through lymph and blood vessels to
other parts of the body. 3
A tumor grows from a single cancer cell. 1
A small percentage of cancer cells may survive and establish a new tumor in another part of the body. 4
Figure 12.19

30. Cancer Treatment Radiation Chemotherapeutic drugs
destroys DNA in cancer cells (so can’t divide)
Chemotherapeutic drugs
interfere with specific steps in cell cycle (Ex: spindle formation or function)
also effects normal cells 
Ex: hair loss

31. Cancer Causing Agents Genetics (inherited) Spontaneous mutation
Envinromental Mutagens (a.k.a- carcinogen)
Sun
Viruses
Chemicals

32. Cancer Animations- REVIEW
Cancer Movie
Called Cancer Quest

33. Flashcard Vocabulary