Wee1

Chapter 12 The Cell Cycle: Practice Quiz Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. Self-Quiz Questions ____ 1. Increases in the enzymatic activity of some protein kinases important for the regulation of the cell cycle are due to a. kinase synthesis by ribosomes. b. activation of inactive kinases by binding to cyclins. c. conversion of inactive cyclins to active kinases by means of phosphorylation. d. cleavage of the inactive kinase molecules by cytoplasmic proteases. e. a decline in external growth factors to a concentration below the inhibitory threshold.