You are studying cell cycle progression in yeast cells. If you could prevent cdc2 from associating with the mitotic cyclin, the cells would:

Question

A.  arrest in G1.
B.  arrest in G2.
C.  arrest in S.
D.  arrest in prometaphase.
E.  arrest in metaphase.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

  Gather Content
  · What do you know about cdc2/cyclin complexes? How does it relate to the question?
  Consider Possibilities  
  · What other information is related to the question? Which information is most useful?

  Choose Answer
  · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

  Reflect on Process
  · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  arrest in G2.

Clarify Question
  · What is the key concept addressed by the question?
        o The question asks about the effect on inhibiting a cdc2/mitotic cyclin complex.
· What type of thinking is required?
        o You are being asked to apply your knowledge of cyclin/cdc2 interactions to predict what would happen if it was inhibited.
· What key words does the question contain and what do they mean?
        o Prevent cdc2 from associating with the mitotic cyclin – cdc2 needs to associate with a cyclin to be active and allow the cell to enter mitosis.  

  Gather Content
  · What do you know about cdc2/cyclin complexes? How does it relate to the question?
        o For a cdc2 kinase to be active it needs to bind to a cyclin. When it is active the cell will proceed to the next stage of the cell cycle.
  Consider Possibilities  
  · What other information is related to the question? Which information is most useful?
        o Because the question specifies a mitotic cyclin, the cdc2/cyclin complex would normally allow the cell to enter mitosis.  Without the complex formation the cell would not enter mitosis, so it could not arrest in a stage of mitosis like prometaphase or metaphase.  Separate checkpoints and cyclins regulate movement of the cell through S and G1.

  Choose Answer
  · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Without a cdc2/mitotic cyclin complex the cell could not enter mitosis.  G2 is the stage before mitosis, so the cell would be stuck in G2.

  Reflect on Process
  · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked you to apply your understanding of the function of the cdc2/mitotic cyclin to predict what would happen if this complex could not form. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you recall that the mitotic cyclin would allow the cell to enter mitosis when bound to cdc2?  Did you realize that G2 is the stage before mitosis, so the cell would be stuck, or arrest, in G2 if this activity was blocked?