Intracelluarly - Mitosis

Question 1

Prophase

Answer 1

The first stage of mitosis where chromosomes condense and the G2 phase ends.

Question 2

What causes chromosomal condensation?

Answer 2

Modifcaitons to the histones the DNA wraps like acetylation and phosphorylation.

Question 3

How does chromosome compaction affect its morphology?

Answer 3

Decrease length and increased thickness.

Question 4

What causes transcriptional shut down during comapction?

Answer 4

TF displacement.

Question 5

What events occur in prophase?

Answer 5

Chromosome Compaction
Nuclear Envelope dispersal
Spindle formation

Question 6

How is rRNA transcription arrested?

Answer 6

Phosphorytlation by CDK1 cyclic B kinase of pol1 TF and NPM/B3.

Question 7

What happens to NPC and lamin fibre components in propase?

Answer 7

CDK1 hyperphosphorylates them.

Question 8

Why is slowing down of protein synthesis during prophase important?

Answer 8

It slows mRNA transit to proect it during mitosis

Question 9

How do cytoskeletal components change during prophase?

Answer 9

MT and microfilaments largely dissolve by PHOS and only actin remains for cytokinesis.

Question 10

How does prophase conserve cytoskeletal material?

Answer 10

Using it to construct spindle and cytokinetic machinery

Question 11

Why is spherical formation after cytoskeltal dissapearance important in prophase?

Answer 11

Promotes symmetrical diffusion for uniform distribution.

Question 12

How is diffusive randomness promoted in prophase?

Answer 12

Decrease of cytoplasmic viscoscity by polymer solublisation.

Question 13

Why are enhanced diffusive capabilities important in prophase?

Answer 13

Equipartinioning of cell resources for cytokinesis.

Question 14

Centrosomes

Answer 14

A cellular organelle of two centrioles, regulating MT formation

Question 15

Prometaphase

Answer 15

This is where nuclear envelope has finalised dispersal and nuclear structures are exposed.

Question 16

What are some of the structural components of the Kinetochore?

Answer 16

NDC80, KNL1, Dyenin and Kinesin.

Question 17

What do motor proteins on MT do?

Answer 17

Influence chromosomes position and MT dynamic instability by force generation.

Question 18

How does dyenin relate to the MC?

Answer 18

It associates its minus end.

Question 19

Merotelic Kinteochore Attachment

Answer 19

An error when a single KC attachs to MT emanaiting from both spindle poles.

Question 20

Why is MT miss-binding common?

Answer 20

There are more tubulins associated with MT walls, thus more chance they bind to KC.

Question 21

What faciliattes KC MT attachment?

Answer 21

Action of Dyenin and Kinesin

Question 22

How does Kinesin assist KC and MT attachment?

Answer 22

It ferries chromosomes towards middle of spindle using parralel adjacent microtubules.

Question 23

How do Dynein and Kinesin work together to facilitate KC and MT attachment?

Answer 23

By reorientation of the chromsome in a way maximising attachment.

Question 24

Spindle Assembly Checkpoint

Answer 24

A mechanism controlling genomic stabiltiy through MT attachment modulation.

Question 25

How does the SAC facilitate its function?

Answer 25

Represses anaphase onset until correct chromosome segregation.

Question 26

What is the mechanism behind SAC activation?

Answer 26

It remains active so long as kinetochore is unattached, thus inhbition occuring when final KC attaches, activating separase

Question 27

Separase

Answer 27

An Enzyme dissolving sister chromatid associations, initiating anaphase.

Question 28

What does Separase target?

Answer 28

CDC20 of APC/C

Question 29

What does separase action result in?

Answer 29

Impediment of CDC20 ability to act on Cyclin B and Securin, which should prevent their destruction.

Question 30

What happens to CDK1 in SAC?

Answer 30

Cyclin B inactives it when Cyclin B is protelysed by CDC20, promoting mitotic exit.

Question 31

How does CDK1 facilitate its function?

Answer 31

Controls mitotic phases by PHOS of regultaors, also restraining proteins later required.

Question 32

Functions of the spindle?

Answer 32

Chromosomal segregation

Question 33

Kinetochores

Answer 33

Mediators of MT and sister chromatid attachment, facilitating correct equtorial segregation.

Question 34

How do KC facilitate with the centromere loci?

Answer 34

CCAN is recruited to CENP-A histone variants

Question 35

Constitutive Centromere-Associated Netowrk

Answer 35

A protein network in the KC, localising to centromeres and facilitating chromatin and MT binding.

Question 36

MT Dynamic Instability

Answer 36

The constant assocaition and disassociation of tubulins from the plus end of the protofilament.

Question 37

What is the general structure of MT?

Answer 37

Beta and Alpha tubulin dimers, plus ends free in the cytoplasm and minus ends anchored.

Question 38

What is MDI mediated by?

Answer 38

GTP hydrolysis of beta tubulins

Question 39

What happens when GTP is hyrdolysed to GDP?

Answer 39

CC where b-tubulin curves outward from the wall of the MT.

Question 40

What happens to A-tubulin in MDI?

Answer 40

GTP remains bound, providing lateral interactions for structural integrity, resisting curvature.

Question 41

What facilitates MTOC MT nucleation?

Answer 41

y-tubulin MT nucleator complex forming open ring models where MT protofilaments stem

Question 42

What is MT polymerisation and depolymerisation facilitated by?

Answer 42

MAPS and Kinesin-13

Question 43

Metaphase

Answer 43

The stage where chromosome pairs are fully condensed and are bound to the mitotic spindle, alligned at the metaphase plate.

Question 44

Metaphase Plate

Answer 44

An equatorial plane of the spindle having chromosomes oriented upon it.

Question 45

How is anaphase onset?

Answer 45

Cohesins cleavage between sister strands

Question 46

Anaphase

Answer 46

Chromosomal segregation and their migration to opposite cell poles.

Question 47

Cytokinesis

Answer 47

Splitting of a cell into two daughter cells.

Question 48

What is the process of cytokinesis?

Answer 48

Cleavage furrow formation, resulting in two daughter cells connected by an intracellular bridge, then bridge absicion.

Question 49

Rab11/FIP3 endosomes

Answer 49

Initate abscission process at the IB in midzone through actin cytoskeltal disassembly.