Cell Cycle 2

Question 1

What are the 4 general events of mitosis?

Answer 1

1. Condensation of chromosomes
2. Assembly of mitotic spindle
3. Breakdown of nuclear envelope
4. Attachment of chromatids to spindle

Question 2

__ is a five subunit protein complex, related to cohesin containing 2 SMC and 3 Non-SMC subunits.

Answer 2

Condensin.

Question 3

The ___ is a bipolar array of microtubules, pulling sister chromatids apart at anaphase.

Answer 3

mitotic spindle.

Question 4

What are the three types of microtubules and what do they do?

Answer 4

kinetochore: attach each chromosome to spindle pole.
interpolar: hold two halves of spindle together.
astral: interact with cell cortex

Question 5

___ is a globular microtubule subunit, a hetero-dimer of alpha and beta tubulin.

Answer 5

tubulin.

Question 6

The __ end of kinetochore microtubules are attached to sister chromatid pairs at large protein structures called kinetochores.

Answer 6

+

Question 7

Plus ends of ___ microtubules, coming from one pole, interact with plus ends from the other pole

Answer 7

interpolar.

Question 8

__ microtubules radiate outward from the poles and contact the cell cortex, helping to position the spindle in the cell.

Answer 8

astral.

Question 9

Microtubules are nucleated from a specific location called the ___.

Answer 9

microtubule-organizing center (MTOC)

Question 10

___ is responsible for the nucleation of MT growth, which occurs at this end of the MT.

What end of the gamma-TURC points outward?

Answer 10

gamma-tubulin ring complex (gamma-TURC).

(-)

(+) end points outward.

Question 11

This protein organelle, ___, consists of matrix and pair of centrioles and greater than 50 copies of gamma-TURCs.

Answer 11

centrosome.

Question 12

Dyneins walk toward the ___ end and towards the center of the cell.

Kinesins walk toward the __ end and tend to move to the periphery of the cell.

Answer 12

minus.

plus.

Question 13

This motor protein, ___, attaches to two MTs that come from opposite ends, in an anti-parallel fashion, and walks toward the plus ends, pushing the spindles (centrosomes) apart.

Answer 13

kinesin-5

Question 14

This motor protein, ___, attaches two MTs that come from opposite poles, and walk toward the minus end, which results in pulling the poles together.

Answer 14

kinesin-14.

Question 15

This motor protein, ___, is a plus directed motor protein that pushes the chromosomes away from the pole. This causes a bend in the chromosomes during anaphase resulting in the push-pull phenomenon.

Answer 15

kinesin-4,10

Question 16

__ is a minus end directed motor protein, linking the plus end of astral MTs to actin skeleton, pulling the spindle poles away from each other.

Answer 16

Dynein.

Question 17

___ are responsible for attachment of spindle to chromosomes, consisting of these anchoring proteins, ___, that attach to MTs. The exposed __ end allows for addition and removal of tubulin subunits and its depolymerization drives the pulling kinetochore forward.

Answer 17

Kinetochore.

Ndc80.

(+)

Question 18

Name the three forces of chromosomal movement

Answer 18

1. Depolymerization
2. Microtubule flex
3. Polar ejection force

Question 19

Describe microtubule flux

Answer 19

Tubulin added at plus end of interpolar MTs while being removed at minus end.

Question 20

M-Cdk activates ___ to complete mitosis.

Answer 20

APC/C

Question 21

During Anaphase A, what happens to the chromosomes?

What happens during Anaphase B?

Answer 21

Chromosomes move apart (due to spindle MT depolymerization at kinetochore).

spindle poles separate (by kinesin-5 and dynein)

Question 22

Actin and myosin compose this, the ___, which exerts enough force to split the cell two.

Answer 22

contractile ring

Question 23

What are the three classes of extracellular signaling molecules that regulate cell size and number?

Answer 23

Class 1: mitogens (stimulate cell division by triggering G1/S-Cdk activity)

Class 2: growth factors

Class 3: survival factors (suppresses apoptosis)

Question 24

Mitogens activate the ___ pathway.

Answer 24

Ras-MAPK

Question 25

Name the 8 steps involved with E2F and the MAP kinase pathway and the two Rb regulatory steps involved.

Answer 25

1. Mitogen binds to receptor
2. Ras causes activation of MAP kinase cascade.
3. Leads to increase of gene regulatory proteins including Myc
4. Myc promotes entry into cell cycle by increasing expression of G1 cyclins and get active G1 Cdk-cyclin.
5. G1-Cdk-cyclin activates group of gene regulatory factors called E2F proteins.
6. E2F binds to promoters of G1/S cyclin and S cyclin genes (DNA xcr)
7. Enter into S phase of cell cycle
8. DNA synthesis begins.

Rb regulatory steps:

1. E2F is inhibited by active Rb protein, shutting down entry into S phase of cell cycle.
2. Active G1-Cdk phosphorylates Rb (now inactive Rb) to reduce Rb binding to E2F. (positive feedback)

Question 26

What if Rb protein is not working?

Answer 26

Then there is no control going into cell cycle and so cancer can occur.

Question 27

Rb is a __, and loss of how many copies leads to retinoblastoma?

What are some characteristics of retinoblastoma?

Answer 27

tumor suppressor.

loss of both copies = no Rb protein made = retinoblastoma.

retinoblastoma occurs before age 2, 95% diagnosed before age 5.

Question 28

DNA damage, like that from X-rays, activates what kinases?

Answer 28

ATM/ATR

Question 29

What steps occur after ATM/ATR kinases are activated from DNA damage?

Answer 29

1. AMT/ATR kinases phosphorylate Chk1 and Chk2 proteins
2. Chk1/Chk2 phosphorylates and activates p53 protein.
3. p53 stimulates xcr of p21
4. p21 is a CKI, binding to G1/S-Cdk and S-Cdk, inhibiting cell division.

Question 30

What two symptoms are seen in AT?

Answer 30

Ataxia = poor coordination.

Telangiectasia = small dilated blood vessels.

Question 31

ATM senses damage to ___. In one case study a patient was diagnosed with AT after 15 chest X-rays. Because the patient had undiagnosed AT,, __ could not function normally and stop the cell cycle or cause apoptosis.

Answer 31

DNA.

p53.

Question 32

This cancer gene, __, is mutated in 30% of cancers.

50% of cancers have a mutation in this gene, ___.

Answer 32

Ras

p53

Question 33

In order for a cell to divide, they also need to grow beforehand. This pathway, ___, is the most important signaling pathway.

Answer 33

PI-3 kinase.

Question 34

PI-3 kinase adds ATP to ___, phosphorylating ___, and activates ___, which activates downstream growth factors.

Answer 34

inositol phospholipids.

PIP2.

TOR.

Question 35

What are the three mechanisms that control cell growth and division?

Answer 35

1. Extracellular factor causes cell growth, which then causes cell division.
2. Cell growth and division controlled separately by growth factors and mitogens.
3. Cell growth and division are both stimulated by extracellular factor.

Question 36

Depletion of ___ can act as a limit on cell division in cell culture. Adding fresh serum can cause the cells to proliferate.

Answer 36

mitogens.

Question 37

___ inhibits muscle cell growth.

Answer 37

Myostatin.