mitosis and cancer part 3 honors genetics ms. gaynor
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Mitosis and Cancer
PART 3
Honors Genetics
Ms. Gaynor
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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
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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
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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
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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
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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
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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.
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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
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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
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M Checkpoint
Makes sure spindle assembly is correct
Makes sure all chromosomes are aligned at the mitotic plate
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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)
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INACTIVE FORM CYCLIN DEPENDENT
KINASE (CDK)
CDK/CYCLIN COMPLEX
CYCLIN
+
ACTIVE FORM
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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
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cyclin degrades & breaks
apart
cyclin degrades & breaks
apart
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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
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Important Cyclins and CDKs
Cyclin D-CDK4
Cyclin E-CDK2
Cyclin A-CDK2
Cyclin B-CDC2
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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
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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
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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
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Internal and External Signals
Internal signalsDNA synthesisGrowth/NutritionCDK/Cyclins
External signalsGrowth factors & HormonesDensity Dependent InhibitionAnchorage Dependence
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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
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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
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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
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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
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Why?
Don’t need growth factors maybe they make their own growth factors
Mutations in GENES!!!Ex: cyclin or Cdk genes
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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!!!
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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
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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
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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
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Cancer Causing Agents
1. Genetics (inherited) 2. Spontaneous mutation3. Envinromental Mutagens
(a.k.a- carcinogen) Sun Viruses Chemicals
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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
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Flashcard Vocabulary
http://highered.mcgraw-hill.com/sites/0078757150/student_view0/vocabulary_eflashcards.html