BIOL211 - L16

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  • Created by: Katherine
  • Created on: 12-04-17 21:46
When in the critical point in regulation in mammalian gells?
The point between GO and G1.
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Can cells enter the cell cycle twice?
Most terminally differentiated cells cannot re-enter the cell cycle, but some fibroblasts can. E.g primary cultures of these cells have a finite life time - i.e. only pass through a small number of division and exhibit contact inhibition grown flat.
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Where is contact inhibition seen
in healthy cells.
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Do cells have infite life?
No they have a finite life time - can only have a certain number of divisions.
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What is contact inhibition?
As cells contact each other, they stop dividing.
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Which cyclin governs the DNA replication stage of the cell cycle?
A and B
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Which cdk and cyclin is found in G1?
Cdk4 and cdk6 and Cyclin D
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Which cdk and cyclin found in s phase?
Cyclin A and cdk2
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Which cdk and cylcin found in g2?
Cdk1 cyclin B and A
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What was the experiment to determine growth factor signalling in quiescen cells?
Serium contains growth factors which cause cells to enter the cell cycle. Across 12 hrs, the mammalian cells divide once.
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What are the early response genes?
The genes which have a first response after addition of serum.
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What does growth factor signalling do?
It activates transcription factors present in the cytoplasm or nucleus.
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What do growth factors cause?
Cell cycle entry cascade
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The growth factors signalling pathways trigger...
The activity of downstream transcription pathways.
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What are the early response genes?
Fos and jun
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What are fos and jun
Transcription factors
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What is the target of fos and jun?
Cyclin D - The end point of the growth factor signalling.
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How are cyclin E and cyclin A expressed?
Rb is on E2F. With the addition of Cyclin D and CDK4/6 the Rb becomes phosphorylated, and comes of the E2B (it dissociates). The expression of cyclin E and A then turns on.
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What are Cyclin E and A used for?
Along with CDK2 they drive the S phase and chromosome duplication.
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What is Rb?
A negative regulator of cell cycle progression: tumour suppressor gene
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What E2F?
Transcriptional activator that controls expression of genes required for DNA replication.
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What makes regulation of the g1 s transition in mammals so quick?
A positive feedback loop
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The more E2F, the more... we produce
Cyclin E
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Which of the genes is a tumour supressor gene?
Rb (retinoblastoma)
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What are D type cyclins?
Early response genes and positive regulatos of cell cycle progression
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Why are Cyclin D and E2F potential oncogenes?
Because genes encoding proteins that drive the cell cycle are potential oncogenes
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What are the features of tumour cells?
Immortal and do not exhibit contact inhibition
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Do tumour cells respond to normal signals during cell division?
Ni
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Do tumour cells require increased amounts of growth factors
No,t he require reduced amounts, often synthesising their own.
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What is homeostasis?
Maintenance of the integrity of tissue and cellular sttucture and function
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What does homeostasis require?
Control of cell division and maintenance of genome stability during cell division and avoidance of mutation: DNA repair mechanisms.
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Tumour cells represent a loss of...
Homeostatic control - this is due to mutation.
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what maintains gene homeostasis?
Cellular anti-proliferative strategies.
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What is checkpoint control?
It links DNA damage/genome integirty to cell division.
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What are antiproliferative strategies?
Checkpoint control and avoidance of unscheduled cell proliferation
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.What is a failure of chromosome segregation
At metaphase, one of the sister chromatids could only segragate to a single pole
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What is checkpoint control?
It recognises improper spindle formation (M arrest), and this triggers a signale to block anaphase transition.
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Why don't you want to go into S phse when you have damaged DNA?
Because you need to repair the nucleau before hand as the polymerases cant deal with it
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What does p53 do?
If the cell percieves damage, p53 is stabilised within the cell.
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If there's DNA damage, the level of P53
increases
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P53 is a
transcription factor.
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What is the target of p53
p21
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What does p21 do?
It is a direct inhibitor of cyclin dependent kinase - it blocks progression at g1 and g2. It's a very simplistic picture of how it works in mammalian cells.
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If you have p53 and cause damage, what is in the s phase?
No DNA replication
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If you have no p53 and cause damage, what is in the s phase?
You still have cells replicating
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Why is replication of DNA damage a problem?
Replicaiton damage can lead to mutation, mutate cell cycle control/check point genes = unregulated cell division and tumour formation.
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Every time a cell divides it mutates at...
A low rate
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Card 2

Front

Can cells enter the cell cycle twice?

Back

Most terminally differentiated cells cannot re-enter the cell cycle, but some fibroblasts can. E.g primary cultures of these cells have a finite life time - i.e. only pass through a small number of division and exhibit contact inhibition grown flat.

Card 3

Front

Where is contact inhibition seen

Back

Preview of the front of card 3

Card 4

Front

Do cells have infite life?

Back

Preview of the front of card 4

Card 5

Front

What is contact inhibition?

Back

Preview of the front of card 5
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