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Molecular BIO > 23 Cell cycle > Flashcards

23 Cell cycle Flashcards

1
Q

What are the three functional aspects of the cell cycle?

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

Three major events that occur in cell cycle are what?

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

Interphase consists of waht phases of cell cycle?

A
  1. G1, S, G2
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4
Q

When does M phase occur?

A
  1. after G2, for only 1 hour. not majority of cell life
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5
Q

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

A
  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
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6
Q

What are fission yeast?

A
  1. model organism for cell cycle study

2. grow at ends by elongation

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7
Q

What are budding yeast?

A
  1. model organism of cell cycle

2. oval yeast, divide by budding

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8
Q

What is cdc gene?

A

cell-division cycle genes

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9
Q

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

A
  1. cyclin dependent kinases can activate specific proteins at the proper time to induce activation
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10
Q

What governs the cell cycle?

A

cyclin-dependent kinases.

– [cdks] does not change over time, only the activity of activating various steps

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11
Q

What is a cyclin?

A
  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
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12
Q

What are the different classes of cyclins?

A
  1. G1/S
  2. S
  3. M
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13
Q

G1/S cyclins

A
  1. activate late G1 cdks

2. level drop in S phase, as we don’t want to trigger starting DNA replication more than once

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14
Q

S cyclins

A
  1. bind cdk after start
  2. chromosome replication
  3. high until mitosis, prevents secondary binding at replication origin or proteins
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15
Q

M cyclins

A
  1. cdks stimulate mitosis entry G2/M checkpoint

2. removed mid-mitosis

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16
Q

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

A
  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
Q

What is the function of Wee1 kinase?

A
  1. adds inhibitory phosphate to Cdk, at the roof site. Cdk is inhibited
18
Q

What is the function of cdc25?

A
  1. removal of roof phosphate to cause activation of Cdk
19
Q

What are CKI?

A

Cdk inhibitory proteins, second method to inhibit Cdk activity

20
Q

When are CKI most commonly used?

A
  1. G1/S and S Cdks
21
Q

What is INK4?

A
  1. CKI of G1 cell cycle phase.

2. mutation leads to hereditary melanoma

22
Q

What are p53 and p21?

A
  1. p53: tumor suppressor gene

2. p21: CKI under direct influence of p53, to stop cell division

23
Q

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

A
  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
Q

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

A
  1. positive feedback loop for activating cdc25, to remove roof phosphate from cdk
  2. inhibition of Wee1 from adding roof phosphate
25
Q

What triggers progression from metaphase to anaphase?

A
  1. protein degradation
  2. facilitated by APC/C (anaphase promoting complex)
  3. ubiquitin ligase
26
Q

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

A
  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
Q

How can cyclin-cdk activity be regulated?

A
  1. cdk phosphorylation
  2. CKI binding
  3. cyclin proteolysis
  4. protein ubiquitination
28
Q

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

A
  1. G1 with formation of PRE-RC, prereplicative complex

2. S phase, during replication fork formation

29
Q

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

A
  1. PRE-RC (prereplicative complex)

2. binds to the replication origin preventing origin proteins from binding

30
Q

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

A

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

31
Q

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

A
  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

Molecular BIO (24 decks)

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