You are studying cell cycle progression in an early frog embryo. If you were to inject a protein synthesis inhibitor into a cell during S phase, where do you predict that the cells would arrest?

Question

A.  G1
B.  G2
C.  Metaphase
D.  Telophase

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 protein synthesis and the cell cycle? 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.  G2

Clarify Question
  · What is the key concept addressed by the question?
        o The question asks about the role of protein synthesis in cell cycle check points.
· What type of thinking is required?
        o You are being asked to apply your knowledge of which proteins need to be synthesized for a cell to move through the cell cycle.
· What key words does the question contain and what do they mean?
        o Protein synthesis inhibitor – if new protein synthesis is inhibited then cyclins cannot be made.

  Gather Content
  · What do you know about protein synthesis and the cell cycle? How does it relate to the question?
        o Cyclins need to be made new for the cell to move through each stage of the cell cycle.  If cyclins cannot be synthesized then the cell will be stuck in that stage of the cell cycle.

  Consider Possibilities  
  · What other information is related to the question? Which information is most useful?
        o By adding the inhibitor in S phase, the cell will already have gone through the G1/S checkpoint.  The next checkpoint is the G2/M checkpoint.

  Choose Answer
  · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Because the protein synthesis inhibitor is added during S phase the next checkpoint is the G2/M checkpoint.  Without newly made cyclin the cell will not be able to pass this checkpoint and will become 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 synthesis of cyclins to predict what would happen if protein synthesis was blocked. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you recall that cells in S phase had already passed the G1/S check point?  Did you remember that the G2/M checkpoint would be next?  Did you understand that cyclins need to be synthesized for cells to pass through each stage of the cell cycle?