Intracellularly - Mitosis Regulation

Question 1

What does CDK1/Cyclin B do in Mitosis?

Answer 1

Phosphorylates nuclear lamins for spindle access to chromosomes, assists in compaction

Question 2

How is the chromosome condensed?

Answer 2

Phosphorylation of the condensin complex on the chromosomes that mediates chromatin condensation

Question 3

What does CDK1/CB do in metaphase?

Answer 3

SAC and KC-MT interaction stabilization.

Question 4

How does CDK1/CB interact with SAC?

Answer 4

Phosphorylates Mad1/2 activating SAC by inhibition of APC/C for correct alignment of chromsomes

Question 5

How does CDK1/CB regulate KC-MT attachment?

Answer 5

Aurora B activity is promoted which is found in the inner centromere, phohsphorylating KC proteins like H3 to promote release of incorrect MT attachments.

Question 6

How is Aurora B enhanced?

Answer 6

INCENP phosphorylation by CDK1/CB to destabilise incorrect attachments

Question 7

How is Mad1/2 recruitment promoted?

Answer 7

CDK1/CB phosphorylation allowing recruitment to KC like KMN network(creates binding sites.

Question 8

What do Mad1/2 proteins?

Answer 8

Inhibition of APC/C until correct chromosomal allignment.

Question 9

How are the correct KC recognised?

Answer 9

Tension mediated process where MT pull on KC transmitting to KMN destablising attachmenets.

Question 10

What are the two cell cycle promoting factors?

Answer 10

S-phase
M-Phase

Question 11

S-Phase Promoting Factor

Answer 11

This promotes transition from G1 phase to S phase being a complex proteins including Cyclin E and CDK2

Question 12

How does SPF form?

Answer 12

Increased levels of Cyclin E, activated by CDK2 phosphorylation

Question 13

What does SPF do?

Answer 13

Activate proteins required for DNA replicaiton initation like Retinoblastoma Protein and E2F TF

Question 14

E2F TF

Answer 14

This activates genes required for DNA replication like DNAP.

Question 15

M-Phase Promoting Factor

Answer 15

This functions to drive cells into the M-Phase from the G2 phase including Cyclin B and CDK1

Question 16

What does MPF complex formation do?

Answer 16

Phosphorylate lamins and NPC proteins breaking down nuclear envelope and mitotic spindle assembly by MAPS activation.

Question 17

What is Cyclin B upregulated regulated by?

Answer 17

Retinoblastoma Protein upregulates E2F

Question 18

What is cell cycle checkpoint progression mediated by?

Answer 18

Cyclin expression as CDK level remain constant throughout mitosis, only their activity enhanced by increased cycline

Question 19

What does MPF do proceeding mitosis?

Answer 19

Promotes cyclin degrading enzymes to remove cyclin

Question 20

How is Cyclin B degraded?

Answer 20

APC/C is a ligase complex where in tandem with CDC20 and CDK1, cylin B is degraded, where ubiquitation marks Cycling for proteasome degradation.

Question 21

What is the structure of the centriole?

Answer 21

Compose with 9 pairs of microtubule triplets with a hollow centre.

Question 22

What is the function of centrioles?

Answer 22

Organise MT and facilitate spindle apparatus assembly.

Question 23

What is centriole assembly mediated by?

Answer 23

Duplication events in G1/S phase regulated by PLK4 and other proteins.

Question 24

What is the process of centriole duplication?

Answer 24

Mother centriole with a daughter formed adjacent by cartwheel prootein complex

Question 25

What happens to the bound centrioles during mitosis?

Answer 25

Seperated by dynein to opposing ends of the cell with mitotic spindle then forming

Question 26

Mitotic Spindle

Answer 26

This is a structure forming during cell divsion and speerating duplicated chromosomes.

Question 27

What are the three types of spindle microtuble?

Answer 27

Kinetochore MT Polar MT Astral MT

Question 28

Kinetochore MT

Answer 28

These seperate the chromosomes

Question 29

Polar MT

Answer 29

These interact with each other and push the spindle poles apart to elongate the cells

Question 30

Astral MT

Answer 30

These anchor the spindle in place to ensure proper oreintation for cell divsion.

Question 31

How are the spindle microtubules regulated?

Answer 31

Dynein and Kinesin

Question 32

What does MT growth involve?

Answer 32

Y-Tubulin Complex and Dynein/Dynactin complex

Question 33

What does Y-tubulin do?

Answer 33

Nucleates the MT, forming a ring-shaped structure being the assembly foundation for MT

Question 34

What doe K-8 and K-13 do for MT growth?

Answer 34

Promote elongation and shrinkage respectively.

Question 35

Why is K-13 shrinkage important?

Answer 35

Removing incorrect attachments and of damaged MT.

Question 36

What do Dynein/Dynactin do in MT growth?

Answer 36

Elongate MT by acnchoring the minus ends and growing to the chromosomes.

Question 37

What does Dynein do?

Answer 37

Mediates movement of spindle apparatus to the cell cortex for chromosomal attachment and allignment, binding the plus end and moving towards the minus end.

Question 38

How does Dynein elongate the MT?

Answer 38

MDI

Question 39

Example of Astral Motors...

Answer 39

Dynein.

Question 40

What doe kinetochore motors do?

Answer 40

Attach chromosomes to MT for tension-mediated cell division.

Question 41

How do KC motors facilitate their function?

Answer 41

K-4 and K-10 being plus-end directed and dynein being minus-end directed

Question 42

What do polar motors do?

Answer 42

These are involved in MT polymerization and cell elongation by pushing MT in opposing directions in metaphase and anaphase.

Question 43

What are examples of polar motors?

Answer 43

K-5, 12 and 13

Question 44

How is sister chromatid segregation mediated by motor proteins?

Answer 44

Dynein interacts with KC of one sister chromatid and moves towards the minus end, pulling attached chromosomes to the poles through MT-dynactin CC interactions

Question 45

What is chromosomal seperation faciliated by?

Answer 45

Pulling by dynein and pushin by kinesin

Question 46

What does Dynein do in Chromsomal Seperation?

Answer 46

KC motors pull chromosomes towards pole with astral motors pulling centrosomes to inner face of PM, both shorterning by MT depolymerisaiton.

Question 47

What does Kinesin do in Chromosomal Seperation?

Answer 47

Pushing by polar motors polymerising MT to drive polar spindles apart, elongation of the cell and cytokinesis.

Question 48

What is the process of Chromatid Seperation?

Answer 48

Cohesin complex seperation by seperases inhibited initially by securin, APC/C destroys securin allowing seperase cleavage.

Question 49

G1 Phase

Answer 49

This is metabolically functional stage of the cell with growth.

Question 50

How is DNA replication prepared for in G1?

Answer 50

CDK4/6:Cyclin D phosphorylates RBP for E2F release and activation of proteins for replicaiton.

Question 51

What is S phase netry prepared by?

Answer 51

Cycle E/CDK2 complex

Question 52

S Phase

Answer 52

This is where DNA replication occurs

Question 53

G2 Phase

Answer 53

This is preparation for mitosis

Question 54

What happens in G2 phase?

Answer 54

Centrosome is replicated in this stage, with replicated chromsomes and intact nuclear envelope, asters formed by MT elongation

Question 55

Why is G2 important?

Answer 55

CDK1/Cyclin B is formed remaining incative, preparing for mitosis

Question 56

What are the phases of the cell cycle?

Answer 56

G1 S G2 M

Question 57

G1 Checkpoint

Answer 57

Determines proceeding into S phase for DNA replication, regulated by RB protein and P53

Question 58

What checks happen in the G1 checkpoint?

Answer 58

Specific cell size DNA damage sensing Cell cycle arrest if DNA dmaage

Question 59

G2 Checkpoint

Answer 59

Regulates entry into mitosis.

Question 60

What checks happen in G2 checkpoint?

Answer 60

Cell Size DNA replication Favourable envrionment

Question 61

What is the key regulator of G2 checkpoint?

Answer 61

CDK1, preventing cell entry into mitosis

Question 62

SAC

Answer 62

This regulates entry of anaphase from metaphase in mitosis, ensuring all chromosomes are attached to mitotic spindles.

Question 63

What is SAC regulated by?

Answer 63

APC/C

Question 64

What does chromsomes misallignment cause?

Answer 64

Signalling events activating SAC, kianses recruited to unattached KC.

Question 65

What happens after SAC activation?

Answer 65

Aurora B phosphorylated and APC/C inhibited, which otherwise degrades securing and Cyclin B1 for seperate activation.

Question 66

Mitogens

Answer 66

These are signals that act from outside the cell to induce mitosis and cell divsiion

Question 67

How do mitogens work?

Answer 67

Binding cell membrane receptors and intiaiting intracellular pathways for cell division and proliferation

Question 68

Why is cell division regulatiion important?

Answer 68

Prevetion of untimley exit from each stage

Question 69

Cytokinesis

Answer 69

This is the physical seperation of the cytoplasm, forming two new daughter cells, in telophase.

Question 70

What does Cytokinesis involve?

Answer 70

Proteins forming a contractile actin ring at centre of cell by force generation.

Question 71

What is contractile actin ring mediated by?

Answer 71

Anillin nucleation with Rho GTPase and other proteins to site.