Mitosis and Cancer

PART 3

Honors Genetics

Ms. Gaynor

Another Type of Cell Another Type of Cell Division: Binary FissionDivision: Binary Fission

Prokaryotes (bacteria)Reproduce by a type of cell division called binary fission

In binary fission, The bacterial chromosome replicates The two daughter chromosomes move

apartOrigin ofreplication

E. coli cellBacterialChromosome

Cell wall

Plasma Membrane

Two copiesof origin

OriginOrigin

Chromosome replication begins.Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell.

1

Replication continues. One copy ofthe origin is now at each end of the cell.

2

Replication finishes. The plasma membrane grows inward, andnew cell wall is deposited.

3

Two daughter cells result.4Figure 12.11

The cell cycle is HIGHLY regulated

The frequency of cell divisionVaries with the type of cell

These cell cycle differencesResult from regulation at the

molecular level http://highered.mcgraw-hill.com/sites/0072495855/student_vie

w0/chapter2/animation__how_the_cell_cycle_works.html

Cell Cycle Checkpoints The clock has specific checkpoints

a critical control point where stop and “go-ahead” signals can regulate cycle

These signals report whether crucial cellular processes up to that specific point have been completed and completed correctly

There are 3 checkpointsG1 checkpointG2 CheckpointM checkpoint

spindle assembly checkpoint

The Cell Cycle Control System

The sequential events of the cell cycle Are directed by a distinct cell cycle

control system, which is similar to a clock

Figure 12.14

Control system

G2 checkpointM checkpoint

G1 checkpoint

G1

S

G2M

G1 Checkpoint

G1 checkpoint

G1G1

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.

G1 Checkpoint Restriction point just before

entry into S phase Checks cell size & original

DNA for damage Makes key decisions

should cell divide or delay division and enter G0 (resting) phase

Most cells stop at this stage and enter a resting state called G0

G2 Checkpoint Checks cell size Triggers start of M phase DNA is frequently

damaged prior to mitosis if this happens, the cell cycle is arrested via inactivation of cell cycle “control” proteins

M Checkpoint

Makes sure spindle assembly is correct

Makes sure all chromosomes are aligned at the mitotic plate

The Cell Cycle Clock: Cyclins and

Cyclin-Dependent Kinases

Two types of regulatory proteins in cytoplasm are involved in cell cycle controlCyclins Cyclin-dependent kinases (Cdks)

INACTIVE FORM CYCLIN DEPENDENT

KINASE (CDK)

CDK/CYCLIN COMPLEX

CYCLIN

+

ACTIVE FORM

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 

cyclin degrades & breaks

apart

cyclin degrades & breaks

apart

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

Important Cyclins and CDKs

Cyclin D-CDK4

Cyclin E-CDK2

Cyclin A-CDK2

Cyclin B-CDC2

Control of Cell Cycle Animations

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.html

Amination #8http://www.cellsalive.com/apop.htm

Programmed Cell Death (Apoptosis)

In apoptosis http://www.biooncology.com/bioonc/research/apoptosis/index.m

Cell signaling is involved in programmed cell death needed to maintain healthy tissues/ cell function

2 µmFigure 21.17

Stop and Go Signs: Internal and External Signals at the

Checkpoints

Both internal (inside the cell) and external (outside the cell) signalsControl the cell cycle checkpoints

Internal and External Signals

Internal signalsDNA synthesisGrowth/NutritionCDK/Cyclins

External signalsGrowth factors & HormonesDensity Dependent InhibitionAnchorage Dependence

Influences on Cell Division

Growth factors & hormonesStimulate other cells to divide

In density-dependent inhibitionCrowded cells stop dividing

Most animal cells exhibit anchorage dependenceIn which they must be attached to a

structure to divideEx: extracellular matrix of a tissue

Cells anchor to dish surface anddivide (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 12.18 A

Cancer cellsExhibit neither density-dependent

inhibition nor anchorage dependenceImmortal cells (if enough nutrients)

Cancer cells usually continue to divide well beyond a single layer, forming a clump of overlapping cells.

Figure 12.18 B

Loss of Cell Cycle Controls in Cancer Cells

Cancer cellsDo not respond normally to the

body’s control mechanismsForm tumors

TUMOR= mass or group of abnormal dividing cells

Why?

Don’t need growth factors maybe they make their own growth factors

Mutations in GENES!!!Ex: cyclin or Cdk genes

Loss of Cell Cycle Controls in Cancer Cells

Cancer cellsNormal cell cancer cells using

process of transformationtransformationForm tumors

Benign “fine”Clump of cells remain at orginal spot

Malignant “mean” “cancer”“cancer”Loose/destroy attachments to other cells they can spread!!!

Malignant tumors These tumors invade surrounding tissues and

can metastasizeExporting cancer cells to other parts of the

body where they may form secondary tumorsUSE BLOOD STREAM and LYMPH VESSELS USE BLOOD STREAM and LYMPH VESSELS

TO SPREAD!!!TO SPREAD!!! http://www.hhmi.org/biointeractive/media/angiogenesis-lg.mov

Tumor

Glandulartissue

Cancer cell

Bloodvessel

Lymphvessel

MetastaticTumor

Cancer cells invade neighboring tissue.

2A small percentage of cancer cells may survive and establish a new tumor in another part of the body.

4Cancer cells spread through lymph and blood vessels to other parts of the body.

3

A tumor grows from a single cancer cell.

1

Figure 12.19

Cancer Treatment

RadiationRadiation destroys DNA in destroys DNA in cancer cells (these cells have cancer cells (these cells have lost ability to repair damage) lost ability to repair damage)

Chemotherapeutic drugs Chemotherapeutic drugs interfere with specific steps in interfere with specific steps in cell cyclecell cycleAlso effects normal cells Also effects normal cells

Cancer Causing Agents

1. Genetics (inherited) 2. Spontaneous mutation3. Envinromental Mutagens

(a.k.a- carcinogen) Sun Viruses Chemicals

Cancer Animations- REVIEW

Cancer Movie http://www.cancerquest.org/index.cfm?

page=3102&lang=english

http://science.education.nih.gov/supplements/nih1/cancer/activities/activity2_animations.htm

Flashcard Vocabulary

http://highered.mcgraw-hill.com/sites/0078757150/student_view0/vocabulary_eflashcards.html