複選題20. During cell cycle, (A) The cyclins are a family of proteins whose concentration increases and decreases throughout the cell cycle (B) If DNA damage is detected in either the G1 or the G2 phase of the cell cycle, cells still can progress through the M phase of the cycle. (C) Different cyclin-dependent protein kinases (CDKs) that phosphorylate substrates essential for progression through the cell cycle (D) DNA synthesis occurs during the GO phase of the cell cycle (E) If DNA damage cannot be repaired, such cells undergo programmed cell death.