lec 40 Flashcards

1
Q

Commitment to cell reproduction (G1 checkpoint)

A

If answer is no –> G0

If answer is yes —> makes G1-Cycline which attaches to G1-Cdk

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2
Q

Synthesis of DNA replication proteins

A

G1-Cdk indirectly activates TFs

G1-Cdk makes phosphorous which acts on the target

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3
Q

G1-Cdk inactivate

A

Rb proteins on the TFs which allow it to go to work

RB is the physical target of G1-Cdk

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4
Q

DNA replication begins at the

A

ORI travels left and right

we have one per 40k bp

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5
Q

What proteins are sitting on the ORIs

A

ORCs and helicases

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6
Q

G1 Cdk second target

A

S-Cdk

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7
Q

S-Cdk targets

A

ORCs (phosphorylates them)

Causes them to fire, creating a replication fork and beginning replication

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8
Q

The ori’s cannot fire

A

A second time

ORCs can only be phosphorylated once

Not enough Helicases available

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9
Q

Centrosome replication (S phase)

A

Need two centrosomes per cell for mitosis

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10
Q

S-Cdk also indirectly activates

A

Centrosome replication with phosphorylation

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11
Q

Purpose of mitosis

A

To replicate the nucleus

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12
Q

How does the cell tell if DNA replication is done

A

If there is any single stranded DNA left, the cell can recognize it

DNA repair could also be a sign

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13
Q

M-Cdk is activated when

A

DNA replication and repair are complete

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14
Q

Failure to pause cell cycle

A

Chromosomes break during anaphase

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15
Q

M-Cdk first target

A

MTs

M-Cdk activates MT regulatory proteins and make the MTs very active and centrosomes move apart

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16
Q

M-Cdk target 2

A

Nuclear lamina

Phosphorylates and is dismantled

17
Q

M-Cdk target 3

A

M-Cdk inactivates and separates nuclear pores

18
Q

Phosphorylation of lamina and pores causes

A

Membrane to separate from chromosomes so that chromosomes can attach

19
Q

M-Cdk target 4

A

Condensin proteins

Activates condensin

20
Q

5th target of M-cdk

A

Myosins are temporarily inactivated

21
Q

Sister chromatid separation (metaphase checkpoint)

Preparation

A

Cohesion proteins= sister chromatids attachment

Kinetochore proteins= microtubule attachment

22
Q

Trigger for sister chromatid separation

A

APC which is activated by M-Cdk

Inhibited by unattached chromosome (which is after metaphase)

23
Q

APC target

A

Cohesions

Destroys them indirectly

24
Q

APC destroys

A

Securin which is attached to separase

25
Separase
Destroys cohesions
26
Exit from mitosis preparation
Complete set of chromosomes at each pole of cell
27
Trigger for exiting mitosis
APC destroys M-Cdk (final target for APC)
28
Once M-Cdk is removed
All phosphates from M-Cdk are also removed and all targets are inactivated
29
Reestablishment of nucleus
Each chromosome gets a coating of Nuclear Lamins and ER membrane as it expands Each chromosome gets its own coating of nuclear envelope
30
Nuclear envelope coating must be
Tight to exclude cytosolic proteins
31
once each Chromosome has a coating
They fuse into a single nucleus
32
Why are nuclear pores important
To allow the nuclear proteins to reimport back into the nucleus but avoid cytosolic proteins by using an NLS signal that only the nuclear proteins use
33
Cytokinesis
Done by actin and myosins M-Cdk places a phosphate on the myosin which inactivates it Once M-Cdk is broken down after mitosis, the inactivating phosphate is removed and myosin can then perform cytokinesis