1-13 Mitosis

Question 1

stages of mitosis

Answer 1

*Interphase: nuclear env intact, no visible chrom

Prophase: chrom consense/visible, bipolar spindle develops
Prometaphase: nuc env dissolves, chrom begin migrate and seen tocontain two chromatids
Metaphase: chrom fully condense and at metaphase plate
Anaphase: centromeres splits, two chromatids pulled opposite poles
Telophase: chrom reach poles and decondense, nucl membrane reforms, cytoplasm starts to divide

*Cytokinesis: cytoplasms division to dive 2 daughter cells

Question 2

Structural maintenance complex (SMC)

Answer 2

2 complexes that organize chrom during mitosis

chrom cohesion: keeps sister chrom together, unsures sisters apportioned into daughter cells, allows for homology mediated repair, degraded at anaphase to allow for seperation

chrom condensation: compacts chroms, organizes chroms for efficient segregation, uses ATP to pump out chrom loops

Question 3

Activation of Mitotic Cyclins

Answer 3

1. CDK1 binds CyclinB
2. CDK1/CyclinB phosphorylated by CDK activating kinase (CAK) and CDK inhibitory kinase (Wee1)
3. CDC25 phosphatase removes inactiavting phosphate from CDK1/cyclinB
4. active CDK1/cyclinB positive feedbacks to activate Cdc25 for further self activation, cdk1/cyclinB also positive feedbacks by inhibiting CDK inhibitory kinase

Question 4

Disassembly of nuclear envelope

Answer 4

interphase: nucleus in tact with lamins lining lumen side of membrane

1. phosphorylation of nuclear pore proteins and lamins
2. degrades membrane and releases chromosomes in prophase/prometaphse
3. de-phosphrylation of nuclear pore preotisn and laminns–>telophase starts to reform around daughter chromosomes
4. fusion of nuclear envolve vesciles in new daughter cell

Question 5

kinetochore

Answer 5

distinct layers of core

1. centromeric chromatin
2. inner kinetochore
3. outer kinetochore
4. EC/SAC/microtubule binders

interface between chrom and microtubule spindle

Question 6

microtubule spindle formation

Answer 6

dynamic assembly/disassembly allows growth at + end

if GFP bound the + end stable and grows, if GDP bound catastrophe dynamic instability

allows for anaphase seperation quick snap

Question 7

motor proteins role in mitosis

Answer 7

regulate spindle formation, microtubule dynamics, chrom alignment

kinesins: + ended motor moves
dyneins: - end motor

Question 8

3 types of mitosis microtubules

Answer 8

1. aster: bind centriole
2. kinetochore: bind at centromere and centriole
3. interpolar: bind centriole and overlap with motor protein and interpolar from other centriole

Question 9

Mitotic checkpoint complex

Answer 9

MCC: wait signal that inhibits APC (anaphase promoting complex), APC required for anaphase progression

1. prometaphase: “SAC on”, chrom unattached to kinetochore, MCC assembly begins
2. metaphase: “SAC off”, MCC assembly inhibits APC until ready
3. APC activation: degreade mitottic cyclins, loss of chrom cohesion, separate sister chromatids

Question 10

APC/C

Answer 10

Anaphse promoting complex

E3 ubiquitin ligase, leads to proteosome mediated degredation, cofactor cdc20 helps specificy targets (cyclinB/cdk1 and securin)

Question 11

securin

separase

Answer 11

securin: inhibitory protein that bind –>
separase: proteolytic enzyme

APC targets securin for Ub-degredation, separase now free to chew up cohesins and promote metaphse to anaphase transition

Question 12

Metaphase to anaphase transition events

Answer 12

• MCC no longer made
• APC radibly becomes active
• APC Ubs: mitotic cylin (CyclinB/cdk1), securin, cohesin in cleaved by separase

Question 13

Anaphase A

Anaphase B

Answer 13

A: shortening of kinetochore microtubules, movement of daughter chrom to poles, forces generated mainly at kinetochores

B: 1. sliding force is generated between interpoalr microtubules from opposites poles to push the poles apart; the interpolar microtubules also elongate 2. a pulling force acts directly on the poles to move them apart

Question 14

Cytokinesis

Answer 14

signals for location of the contractile ring come from SPINDLE CORTEX interactions and SPINDLE MIDZONE

actinomysin ring pinches off

CyclinB/CDK1 inhibits pinching off

Question 15

types of errors in chromosome attachment

Answer 15

1. amphitelic: goal, all good
2. syntelic: both chromatids pulled to one side by two spindles
3. monotelic: both chromatids pulled to one side by one spindle
4. Merotelic: splits into 3 with one chromatide that was left in middle now making own cell

Question 16

Types of errors in chromosome segregation

Answer 16

1. SAC mutations, inappropriate spindles formed/attached
2. premature loss of chromatid cohesion, sister chromatids both go to same cell
3. aberrant kinetochore attachements, goofy splitting
4. supernumary centrsomes, tries to split in too many different ways, tumor cells will do this

all result in aneuploidy