Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BMS379 - Cancer Biology > L5 - Limitless Replicative Potential > Flashcards

L5 - Limitless Replicative Potential Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Why is C.elegans a useful model system

A

We know the lineage of all 959 cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Cells appear to count …

A

The number of population doublings (generations)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What did Hayflick demonstrate?

A

That cells dont grow forever

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the graph whe looking at the number of population doublings

A

S shaped graph

Initailly (1) slow cell growth 
Then rapid (phase 2) cell growth

Cells then reach a point of senescence (this is known as the Hayflick limit) where cells NO LONGER DIVIDE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How many population doublings does it take to reach the Hayflick limit

A

Around 60

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What can be seen if take cells from older donors regarding the doubling number

A

Doubling number tends to decline with age

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What would be seen if you take cells that have doubled say 30 times and then freeze them …

What conclusions can be made from this

A

That cells will only go through another 30 divisions before they begin to senesce

In other words the cells remember where they are … and always bein to senesce at the same cumulative number of days

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What gene can be used to overcome the senescence block

A

SY40 large T antigen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe how the large T gene could be introduced into cells in a way that it could be easily turned on

A

Transfect cells with a plasmid containing the large T gene

Use an inducible promotoer - e.g. glucocorticoid and then add dexamethasone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Give an example of a compund that would actvviate a glucocorticoid pormoter

A

Dexamethasone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Once dexa has been added how can you verify that transfection has occured

A

Add dex and detect large T through immunoblotting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe what happens to cells in the presence of dex

A

Cells grow as normal until the crisis point - many die but around 1 in 10 emerge and are now immortalised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe what happens to the cells if dex is taken away at any time

A

Cells senesce

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The fact that cells senesce at any time if dex is withdrawn suggests what?

A

There must be a second block to immortal cell growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Cance cells must become ______ for

A

Immortal for tumours to form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How many cells are required in a tumour for it to be fatal?

A

10^12

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why is the fact that 10^12 cells are needed for a tumour to be fatal strange?

A

This is ONLY 40 doublings and is well below the Hayflick limit

WHAT then is the point of senescnce??

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the real story of how cells grow in a tumour

A

Alot of cell death - not true exponential cell growth

After 12 doublings there are around 5 cells not 2048

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the reasons for the huge ammount of cell death within tumours

A

Deprivation of growth factors
Lack of vasculature
Deprivation of oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What assay may be performed to detect cells underogiing apoptosis and their progression through apoptosis

A

Tunnel assay

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe how the tunnel assay works

A

Enzyme that recognises chromosomal fragmentation - label with a flurophore
More fragmentation that occurs means the cells is further into apoptosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Levels of what protein increases as the Hayflick limit is approached?

How can this be visualised

A

P16
P21

Western Blotting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe the actin cytoskeleton in normal cells and senescent cells

A

See a huge increase in the number of stress fibres in senescent cells

24
Q

What is the effect of transfecting P16 into early human endometrial fibroblasts

A

Increase in stress fibres

Now has the morphology of a late cell

25
Q

Describe the effect on senescence of the elimination of p53

A

Decrease in p53

26
Q

How was p53 eliminated

A

Expose to a virus encoding a p53 siRNA

27
Q

How was p53 knockdown confirmed

A

Using western blot

28
Q

What were the results of p53 knockdown

On P21 and p16

On the ammount of cells going through apoptosis

A

Decrease in P16 p21

Decrease in the number of cells going through apoptosis

29
Q

What is the function of P16

A

Binds to the catalytic of cdk4 and cdk6

Tweaks the regions to prvent ATP binding - so now no longer able to function as a kinase

30
Q

Where does p16 act

A

At the restriction point

31
Q

Where does p21 act

A

At the G1/S transition

32
Q

What is the function of both Cdk4 and cdk6

So what occurs if they are inhibited by P16/21

A

Phosphorylation of Rb –> leads to the expression of E2F target genes - without this Rb not phosphorylated and E2F genes not transcribed

33
Q

What is the action of P16 and P21 dependent on

What happens in cells when this critical component of the pathway is missing?

A

function of Rb

Where there is no Rb - senescence is not possible

34
Q

What provides a basis for the ability of a cell to count its divisions

A

Teleomers

35
Q

What is the function of telomeres

A

Prevent cell death from arising due to chromosomal end-to-end fusion

36
Q

Describe how you could test the absence of chromosomes

A

Deletion of essential telomere protein TRF2

37
Q

What is the results of a deletion of Trf2

A

Loss of telomeres
Chromosomes join together with multiple centromeres
Problems during segragation - breakage occurs at molecular weak points
End result is chromosomal end swapping

38
Q

What are telomeres composed of

A

Hexomeric repeates of TTAGGG

Gives a G and C rich strand

39
Q

What strand provides the single strand overhang

A

3’ G rich strand

40
Q

How to telomers preserve chromosomal integrity

A

Looping able to occur - 3’ end tucked up into a loop

T-LOOP forms

41
Q

How then are telomeres able to function as a clock

A

Their is leading and lagging strand synthesis
At the 5’ end - lagging strand, RNA primer doesn’t quite fit perfectly so at the end of every cycle the telomere will shorten

42
Q

Describe how you would measure chromosomal end shortening

A

Extract chromosomal DNA
Restrict with multiple enzymes that do not target TTAGGG
Run DNA electrophoresis
Transfer to membrane
Label with DNA probe antisense to the telomere
Souther blotting - visuaise with AUDIORADIOOGRAPHY

43
Q

What can be seen regarding the length of telomeres and time

A

Telomere length shortens as a function of time

44
Q

What is responsible for the replication of telomeres

A

Telomerase

45
Q

What is telomerase

A 
A DNA polymerase of the reverse transcriptase class 
RNA --> DNA
46
Q

What is unique about telomerase

A

It has its own template

47
Q

What could be used to measure telomerase activity

A

TRAP assay

48
Q

What can be said of the telomerase activity of an immortal cell

A

Has increased telomerase activity

49
Q

What is hTERT

A

The catalytic subunit of telomerase reverse transcriptase

50
Q

What may be avoided by expressing HTERT in cells

A

Crisis may be avoided

51
Q

Describe how telomerase activity could be targeted for therapeutic benifit

A

Tumour cell growth can be blocked by interfering with telomerase function
If immortalisation via telomerase expression is important for tumorigenesis
Cancer cell proliferation might be blocked by interfering with telomerase activity

52
Q

What correlation was seen following transfection of HTERT

A

Length of time following transfection to see an inhibition of cell growth is a function of the length of the teleomeres in cells

53
Q

What cancer types can telomerase expression be used as a prognostic marker for

A

Neuroblastoma and Ewings Sarcoma

54
Q

What is seen in cancers that have negative/low telomerase levels

A

Prognosis is quite good

55
Q

Why s it the case that many neuroblastomas fail to transit to immortality

A

Early neuroblastomas have not yet gone through crisis

So … many neuroblastomas dont transit to immortality

BMS379 - Cancer Biology (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions