cell cycle regulation and cancer lecture #20 honors biology ms. day
TRANSCRIPT
Cell Cycle Regulation and Cancer
Lecture #20
Honors BiologyMs. Day
Another Type of Cell Division: Another Type of Cell Division: Binary FissionBinary Fission
Prokaryotes (bacteria)Reproduce by a type of cell division called binary fission No nucleus no karyokinesis!!
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
Cell Cycle needs to be controlled
(Regulated) The cell cycle has 3 checkpoints
A place where stop and go signals can regulate (control) cycle
Signals report if things up to that specific point have:
been completed and completed correctly
There are 3 checkpointsG1 checkpointG2 CheckpointM checkpoint
The Cell Cycle Control System
Figure 12.14
Control system
G2 checkpointM checkpoint
G1 checkpoint
G1
S
G2M
Checkpoint = give “go” or “stop” signals
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.
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.html
•Chromosomes are lined up in the middle properly
of replicated DNA
of unreplicated (original) DNA
What controls the checkpoints?
Two types of proteins in cytoplasmCyclins 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
Programmed Cell Death (Apoptosis)
If cell doesn’t “pass” checkpoint, it goes through apoptosis
http://www.dnatube.com/video/1188/Apoptosis-animation Cell signaling is involved in programmed cell death needed to
maintain healthy tissues/ cell function
2 µmFigure 21.17
http://bio-alive.com/categories/apoptosis/
apoptosis.htm
What other things control cell division?
Both internal and external signals control the cell cycle/cell division…Internal signals
CDK/Cyclins at checkpointsExternal signals
Growth factorsDensity dependent inhibitionAnchorage dependence
External (outside the cell) Influences on Cell Division
Growth factorsStimulate other cells to divide
In density-dependent inhibitionCrowded cells stop dividing
Most animal cells exhibit anchorage dependenceCells must be attached to a structure to
divideEx: protein of a tissue or another cell
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 cellsDo NOT follow the “rules”
No checkpoints and no density-dependent inhibition or anchorage dependence
Immortal 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 cells form tumorsTUMOR= mass or group of
abnormal dividing cells
Types of Tumors Cancer cells form tumors
Benign “fine”Clump of cells remain at orginal spot
Malignant “mean” “cancer”“cancer”Loose/destroy attachments to other cells they can spread or move (called metastasize)!!!
Why?Don’t need growth factors maybe
they make their own growth factorsMutations in GENES that make proteins involved in control systems!!!
Cancer Movie http://www.hhmi.org/biointeractive/using-p53-fight-cancer http://www.cancerquest.org/index.cfm?page=3102&lang=english
Cancer cells are “hungry”…
Angiogenesis is the recruitment of blood vessels from
the network of neighbouring vessels. Without blood and the nutrients it carries,
a tumor would be unable to continue growing.
http://www.hhmi.org/biointeractive/angiogenesis
Cancer Treatment
Radiation Radiation 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
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
Angiogenesis (the formation of new blood vessels)
and Metatasis
http://www.hhmi.org/biointeractive/media/angiogenesis-lg.mov
http://www.hhmi.org/biointeractive/media/vegf-lg.mov