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Stem cells > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

what are the 3 choices stem cells can make?

A

1) self renewal
2) differentiation
3) death

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2
Q

what are the 3 major steps of the cell cycle?

A

1) cell growth and chromosome replication
2) chromosome segregation
3) cell division

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3
Q

what are the 4 phases of the cell cycle?

A

1) G1 phase
2) S phase
3) G2 phase
- first 3 steps are interphase
4) mitosis

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4
Q

what 3 things happen in the G1 phase?

A
  • cell increases in size
  • RNA is produced
  • prep for DNA synthesis
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5
Q

what 2 things happen in the S phase?

A
  • DNA is synthesised

- chromosomes duplicated

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6
Q

what 2 things happen in the G2 phase?

A
  • cell checks fidelity of DNA

- prep for nuclear division

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7
Q

what are the 5 phases of mitosis?

A

1) prophase
2) prometaphase
3) metaphase
4) anaphase
5) telophase

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8
Q

what are 3 basic components which regulate the cell cycle?

A

1) cyclin dependent kinases
2) cyclins
3) CDK inhibitor proteins
(CDK complexes)

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9
Q

what are 2 differences about the expression of each cyclin in mammals?

A

1) they are each limited to a specific cell cycle phase

2) each binds to a specific CDK partner

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10
Q

what is the role of cyclin D?

A

direct link between the extracellular environment and the cell cycle - most growth factors act by directly up-regulating cyclin D expression ie promoting self renewal

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11
Q

what phase are cyclin D+E linked with?

A

G1 phase

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12
Q

what phase in cyclin A linked with?

A

S phase

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13
Q

what phase in cyclin B linked with?

A

Mitosis

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14
Q

what is the restriction point?

A

point of no return the cell is committed to complete the remainder of the cell cycle or exit into G0

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15
Q

what does the ink4 family do?

A

inhibit CDK4 - preventing cyclin binding

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16
Q

what does the KIP family do?

A

CDK inhibitor protein - prevent cyclin-CDK activation

17
Q

what is different between pluripotent stem cell cycles and somatic cell cycles?

A

in PSCs the G1 phase is shorter and S phase is longer- this is because they don’t have a long restriction point in G1 if any damage is observed they just trigger apoptosis - their turnover of division is fast enough and it avoids any mutations occurring throughout the embryo

  • self renewal is maintained in S phase and differentiation is prevented
18
Q

what is G0?

A

when the cell is in quiescent state. G0 phase is sometimes viewed as an extended G1 phase, where the cell is neither dividing nor preparing to divide.

19
Q

what is the key cell cycle transition point?

A

G1/S

20
Q

what are cells sensitive to in G1?

A

different signals

21
Q

when does self renewal control?

A

S/G2

22
Q

what is Apoptosis?

A

programmed cell death

23
Q

what can malfunction of apoptosis lead to?

A

disease

24
Q

what is apoptosis role in stem cells?

A 
too much (tissue atrophy) - problems with regeneration by loss of stem cells  
too little (hyperplasia) - problems with function  - too many stem cells
25
Q

what is the difference between apoptosis and necrosis?

A

apoptosis is purposeful cell death whereas necrosis is accidental cell death
apoptosis = shrinking of cytoplasm and nuclear condensation - mitochondria release death signals
necrosis = swelling of cytoplasm - total cell lysis - disintegration of organelles

26
Q

what are 2 things which make a cell decide to commit suicide?

A

1) withdrawal of positive signals

2) presence of negative signals

27
Q

what are 2 apoptosis pathways?

A

1) intrinsic - intracellular proteins - inhibit or promote apoptosis DNA damage
2) extrinsic - signal comes from surrounding cells by death ligands which bind and initiate caspase cascade

28
Q

what are 4 typical features of cancer stem cell cycles?

A

1) cannot arrest at G0
2) failure to respond appropriately to growth factor signals
3) cells do not have limited replicative life span
4) loss of G1/S restriction point control

29
Q

what are caspases?

A

family of proteases - molecules which cause apoptosis

Stem cells (15 decks)

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