lec 40

Question 1

Commitment to cell reproduction (G1 checkpoint)

Answer 1

If answer is no –> G0

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

Question 2

Synthesis of DNA replication proteins

Answer 2

G1-Cdk indirectly activates TFs

G1-Cdk makes phosphorous which acts on the target

Question 3

G1-Cdk inactivate

Answer 3

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

RB is the physical target of G1-Cdk

Question 4

DNA replication begins at the

Answer 4

ORI travels left and right

we have one per 40k bp

Question 5

What proteins are sitting on the ORIs

Answer 5

ORCs and helicases

Question 6

G1 Cdk second target

Answer 6

S-Cdk

Question 7

S-Cdk targets

Answer 7

ORCs (phosphorylates them)

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

Question 8

The ori’s cannot fire

Answer 8

A second time

ORCs can only be phosphorylated once

Not enough Helicases available

Question 9

Centrosome replication (S phase)

Answer 9

Need two centrosomes per cell for mitosis

Question 10

S-Cdk also indirectly activates

Answer 10

Centrosome replication with phosphorylation

Question 11

Purpose of mitosis

Answer 11

To replicate the nucleus

Question 12

How does the cell tell if DNA replication is done

Answer 12

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

DNA repair could also be a sign

Question 13

M-Cdk is activated when

Answer 13

DNA replication and repair are complete

Question 14

Failure to pause cell cycle

Answer 14

Chromosomes break during anaphase

Question 15

M-Cdk first target

Answer 15

MTs

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

Question 16

M-Cdk target 2

Answer 16

Nuclear lamina

Phosphorylates and is dismantled

Question 17

M-Cdk target 3

Answer 17

M-Cdk inactivates and separates nuclear pores

Question 18

Phosphorylation of lamina and pores causes

Answer 18

Membrane to separate from chromosomes so that chromosomes can attach

Question 19

M-Cdk target 4

Answer 19

Condensin proteins

Activates condensin

Question 20

5th target of M-cdk

Answer 20

Myosins are temporarily inactivated

Question 21

Sister chromatid separation (metaphase checkpoint)

Preparation

Answer 21

Cohesion proteins= sister chromatids attachment

Kinetochore proteins= microtubule attachment

Question 22

Trigger for sister chromatid separation

Answer 22

APC which is activated by M-Cdk

Inhibited by unattached chromosome (which is after metaphase)

Question 23

APC target

Answer 23

Cohesions

Destroys them indirectly

Question 24

APC destroys

Answer 24

Securin which is attached to separase

Question 25

Separase

Answer 25

Destroys cohesions

Question 26

Exit from mitosis preparation

Answer 26

Complete set of chromosomes at each pole of cell

Question 27

Trigger for exiting mitosis

Answer 27

APC destroys M-Cdk (final target for APC)

Question 28

Once M-Cdk is removed

Answer 28

All phosphates from M-Cdk are also removed and all targets are inactivated

Question 29

Reestablishment of nucleus

Answer 29

Each chromosome gets a coating of Nuclear Lamins and ER membrane as it expands

Each chromosome gets its own coating of nuclear envelope

Question 30

Nuclear envelope coating must be

Answer 30

Tight to exclude cytosolic proteins

Question 31

once each Chromosome has a coating

Answer 31

They fuse into a single nucleus

Question 32

Why are nuclear pores important

Answer 32

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

Question 33

Cytokinesis

Answer 33

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