E3L6: Cell Cycle II

Question 1

Which of the following are TRUE regarding laminin?

A. It composes the nuclear lamina

B. It is an intermediate filament

C. It is a substrate of mCDK

D. It breaks down when phosphorylated

E. None of the above are true

Answer 1

E. None of the above are true!

All those choices describe LAMINS not LAMININ!

(Laminin is a basal lamina protein, whereas lamins compose the inner nuclear envelope)

Question 2

*critical thinking*

The inhibition of mCDK has what effect on microtubule formation?

A. MAP remain unphosphorylated, thus unable to suppress catastrophe

B. Kinesin 13 remains unphosphorylated, thus unable to promote catastrophe

C. The probability that MT’s will reach kinetochores will increase

D. A and B

Answer 2

D. A and B

Both MAP and Kinesin 13 is a substrate of mCDK.

Question 3

How many kinetochores are there in a cell?

A. 23

B. 46

C. 92

E. 21

Answer 3

C. 92

Question 4

Which of the following MT’s interact with the plasma membrane?

A. Astral MT’s

B. Kinetochore MT’s

C. Interpolar MT’s

D. They all interact with the PM

Answer 4

A. Astral MT’s

Question 5

During anaphase, which MT’s push the centrosomes away from each other?

A. Astral MT

B. Kinetochore MT

C. Interpolar MT

D. They all do that.

Answer 5

C. Interpolar MT’s

Question 6

Which protein is responsible for holding sister chromatids together?

A. Condensin

B. Cohesin

C. Integrin

D. Lamin

Answer 6

B. Cohesin

Question 7

Which of the following is FALSE regarding the kinetochore?

A. It contains at least 12 proteins

B. H3 variant CENPA

C. Hyperacetylated histones

D. Hypermethylated histones

Answer 7

C. Hyperacetylated histones

(should be unacetylated)

Question 8

Which of the following is a kinase that surveys DNA damage?

A. p53

B. ATM/ATR

C. p21

D. Chk1/Chk2

Answer 8

B. ATM/ATR

Question 9

Which of the following are ubiquitinated by APC? Circle all that apply.

A. M-cyclin

B. Securin

C. Separase

D. Cohesin

Answer 9

A. M-cyclins

B. Securins

Question 10

Which of the following can activate APC, to begin anaphase?

A. CDC-20 (phosphorylated)

B. CDC-20

C. Cdc25

D. CKI

Answer 10

A. Cdc20 (phosphorylated)

Question 11

Cdc20 activation is likely due to

A. Positive signals from attached kinetochores

B. Negative signals from unattached kinetochores

Answer 11

B. Negative signals from unattached kinetochores

Positive signaling system would be too weak to recognize the 92nd positive signal above 91 already generated positive signals. But single inhibitory signal could be sensed and deciphered.