FOM 7.4.1

Question 1

What are the phases of mitosis?

Answer 1

Prophase, Metaphase, Anaphase, Telophase

Question 2

What happens in early/late prophase?

Answer 2

Early: condensation of replicated chromosomes Late: MT have self-assembled and replicated centrosomes move apart

Question 3

What happens in prometaphase?

Answer 3

Break down of nuclear envelope, allowing spindle MT to interact w/ condensed chromosomes

Question 4

What happens in metaphase?

Answer 4

Chromosomes are aligned along equator forming metaphase plate and bipolar spindle is clear

Question 5

What happens in early/late anaphase?

Answer 5

Early: cohesins degrade, sister chromatids seperate, daughter chromosome move toward poles Late: Spindle poles move farther apart, enhancing separation of chromosomes

Question 6

What happens in telophase?

Answer 6

Formation of daughter nuclei

Question 7

What type of tubulin helps organize MT at the centrosome?

Answer 7

Gamma

Question 8

Describe the polymerization of tubulin?

Answer 8

Very dynamic (standard life span is 33s)

Question 9

What are the three types of MT involved with mitosis? Their function?

Answer 9

Overlap MT: provide spindle structure and interacts w/ opposing overlap MT Astral MT: anchors the centrosome Kinetochore MT: Bind at kinetochore/centromere

Question 10

What is know as the MT organizing center? What is it surrounded by?

Answer 10

Centrosome, pericentriolar material

Question 11

What is the mother centrosome? Where is found?

Answer 11

The centrosome that is present during all phases of the cell cycle, helps organize primary cilia. It is found in cytoplasm attached or close to the nucleus during interphase.

Question 12

When is the centrosome duplicated?

Answer 12

S phase (Just like the DNA, Miles)

Question 13

What tightly regulates centrosome function?

Answer 13

Proteins of the pericentriolar matrix

Question 14

Which protein is responsible for causing mitotic arrest or cell death if polarity of the centrosome is abnormal?

Answer 14

p53

Question 15

What are two important facts about the kinetochore in relation to its function during mitosis?

Answer 15

Stabilizes plus end of MT, binds to centromere

Question 16

What portion of the kinetochore is responsible for stabilization of the + end of the MT?

Answer 16

Dam Complex

Question 17

What is the special type of histone protein that is recognized by the kinetochore influencing its attachment to the centromere?

Answer 17

CENPA

Question 18

What are three mitotic kinases that control spindle formation? Their location?

Answer 18

Aurora Kinase A (centrosome), Polo Like Kinase (centrosome and kinetochore), Aurora Kinase B (kinetochore/spindle midzone)

Question 19

When is the Spindle Assembly Checkpoint (SAC) turned on?

Answer 19

SAC is turned on until there is proper attachment to both kinetochores, one on each side. SAC signals to MCC to stop progression until spindle is properly assembled.

Question 20

What does APC stand for?

Answer 20

Anaphase Promoting Complex

Question 21

What inhibits the APC?

Answer 21

The Mitotic Checkpoint Complex (MCC), which is composed of BUBR1 and BUB3

Question 22

What sequentially degrades cyclins and mitotic kinases to push the cell through mitosis?

Answer 22

Anaphase Promoting Complex (APC)

Question 23

What are responsible for provided the force to pull apart the spindle?

Answer 23

Kinesin, Dynein, and Myosin (just a reminder: they use ATP hydrolysis to provide energy to walk)

Question 24

What is surrounds the midbody? (The midbody is the middle area in b/t the two centrosomes that have the chromosome towards them)

Answer 24

An actin ring

Question 25

What regulates the actin contractile ring that pinches the two daughter cells apart?

Answer 25

Aurora B and PLK

Question 26

What is the molecular function of Taxol (from the Pacific Yew)? Why is this good as a first-line therapy against cancer?

Answer 26

Stabilize tubulin; by not allowing for the destabilization, spindles start getting stuck preventing formation of a functional spindle that induces cell death due to prolonged spindle assembly checkpoint.

Question 27

Look at these two slides to better understand how the checkpoints interact with one another.

Answer 27

Question 28

What is the process of the spindle assembly checkpoint?

Answer 28

When there is an unattached kinetochore, MAD2 binds to the open region. MAD2 then binds to CDC20 which is part of SAC. The other part of SAC is the APC. MAD2 and CD20 binding to SAC leads to recruitment of the MCC (BubR1 and Bub3). Which will cause dissociation of MAD2 from the SAC. The MCC binding will cause the APC to be inhibited and cannot carry out normal functions of degrading cyclin B and securin. When the there is proper alignment of the chromosones MAD2 will not interact with CD20, and eventually MCC will dissociate from APC and the APC will now be active and can degrade its proper targets