The movement of cells from G-1 in the cell cycle into S-phase is mostly under the control of:

W) cyclins and cyclin-dependent kinases

X) the availability of purines and pyrimidines

Y) ubiquitin (read as: you-BIK-qui-tin) and proteosomes (read as: PRO-tee-oh-somes)

Z) G proteins and APC's
W) CYCLINS AND CYCLIN-DEPENDENT KINASES