[Campbell Biology P.294] Which of the following statements about cyclins, cyclin-dependent k... | Practice Question

Which of the following statements about cyclins, cyclin-dependent kinases Cdks , and MPF are correct? Select all that apply

  • A: Cyclins are protein kinases that activate or inactivate other proteins by phosphorylating them.
  • B: Cyclin-dependent kinases (Cdks) are present at a constant concentration in the growing cell but are only active when bound to a cyclin.
  • C: MPF activity peaks during the S and G2 phases, leading to the initiation of mitosis.
  • D: MPF is a cyclin-Cdk complex that triggers the cell's passage into the M phase.

Explanation

Option B is correct as the text states Cdks are 'present at a constant concentration in the growing cell, but much of the time they are in an inactive form. To be active, such a kinase must be attached to a cyclin'. Option D is also correct, as the text defines MPF as 'the cyclin-Cdk complex' that 'triggers the cell's passage into the M phase, past the G2 checkpoint'. Option A is incorrect because Cdks are protein kinases, not cyclins. Option C is incorrect because MPF activity peaks during the M phase, not S and G2 phases.