23 Cell cycle Flashcards Preview

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Flashcards in 23 Cell cycle Deck (31):
1

What are the three functional aspects of the cell cycle?

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

2

Three major events that occur in cell cycle are what?

1. S phase: DNA replication
2. M phase: chromosome segregation and cell division
3. cytokinesis

3

Interphase consists of waht phases of cell cycle?

1. G1, S, G2

4

When does M phase occur?

1. after G2, for only 1 hour. not majority of cell life

5

Where are the regulatory control points that permit/inhibit cell cycle progression?

1. Start checkpoin from G1 into S phase (restriction point)
2. G2/m phase: proper chromosome alignment in metaphase
3. met-anaphase check: triggers chromatid separation and cytokinesis

6

What are fission yeast?

1. model organism for cell cycle study
2. grow at ends by elongation

7

What are budding yeast?

1. model organism of cell cycle
2. oval yeast, divide by budding

8

What is cdc gene?

cell-division cycle genes

9

What is used to activate various steps of the cell cycle?

1. cyclin dependent kinases can activate specific proteins at the proper time to induce activation

10

What governs the cell cycle?

cyclin-dependent kinases.
-- [cdks] does not change over time, only the activity of activating various steps

11

What is a cyclin?

1. protein that regulates the activity of cdks
2. [cyclins] subject to change in order to adjust activity of cdks
3. specific to the point in the cell cycle

12

What are the different classes of cyclins?

1. G1/S
2. S
3. M

13

G1/S cyclins

1. activate late G1 cdks
2. level drop in S phase, as we don't want to trigger starting DNA replication more than once

14

S cyclins

1. bind cdk after start
2. chromosome replication
3. high until mitosis, prevents secondary binding at replication origin or proteins

15

M cyclins

1. cdks stimulate mitosis entry G2/M checkpoint
2. removed mid-mitosis

16

The cdks have activation by cyclins, and what else has to occur in order to fully activate them?

1. cdk-activating kinase must act to remove the T-loop from the active site of the cyclin, to allow full activation of cdk

17

What is the function of Wee1 kinase?

1. adds inhibitory phosphate to Cdk, at the roof site. Cdk is inhibited

18

What is the function of cdc25?

1. removal of roof phosphate to cause activation of Cdk

19

What are CKI?

Cdk inhibitory proteins, second method to inhibit Cdk activity

20

When are CKI most commonly used?

1. G1/S and S Cdks

21

What is INK4?

1. CKI of G1 cell cycle phase.
2. mutation leads to hereditary melanoma

22

What are p53 and p21?

1. p53: tumor suppressor gene
2. p21: CKI under direct influence of p53, to stop cell division

23

The protein SCF-ubiquitin ligase has what role in cell cycle?

1. adds ubiquitin to proteins, to mark them for degradation
2. can add to CKI, to promote cell division
3. F box protein is rate determining factor

24

The activation of M-Cdk has what effect in terms of regulation?

1. positive feedback loop for activating cdc25, to remove roof phosphate from cdk
2. inhibition of Wee1 from adding roof phosphate

25

What triggers progression from metaphase to anaphase?

1. protein degradation
2. facilitated by APC/C (anaphase promoting complex)
3. ubiquitin ligase

26

What major proteins are affected during anaphase, when the APC/C is activated?

1. securin is degraded, which protects cohesin from degradation
2. cohesin is degraded, which holds the sister chromatids together until this point to allow for separation

27

How can cyclin-cdk activity be regulated?

1. cdk phosphorylation
2. CKI binding
3. cyclin proteolysis
4. protein ubiquitination

28

At what phases of cell cycle is chromosome duplication under control?

1. G1 with formation of PRE-RC, prereplicative complex
2. S phase, during replication fork formation

29

What assembles during G1 phase to ensure on 1 copy of DNA is made?

1. PRE-RC (prereplicative complex)
2. binds to the replication origin preventing origin proteins from binding

30

What assembles during S phase of cell cycle to control chromosome duplication?

1.replication forks, prevent complete trascription/copying of DNA strand

31

PRE-RC is preset in G1 phase, what prevents this protein from being present during S and M phase of cell cycle?

1. cdks inhibit the formation of PRE-RC during S and M phase.
2. deletion of all cdks is required before entering G1, so PRE-RC can regain function and only allow 1 round of chromosomal copying