Answer: Activating Cdks (cyclin-dependent kinases) at specific stages.
- A Directly cutting and degrading chromosomal DNA strands
- B Activating Cdks (cyclin-dependent kinases) at specific stages
- C Forming and polymerizing the mitotic spindle fibers
- D Causing chromosome condensation independently of Cdks
Correct answer: B. Activating Cdks (cyclin-dependent kinases) at specific stages
Explanation: Cyclins rise and fall during the cell cycle. They activate Cdks, which phosphorylate target proteins to drive cell cycle progression.
The cell cycle: G1 (growth and preparation), S (DNA replication, chromosome number stays 2n but DNA content doubles), G2 (final checks before division), and M (mitosis itself) - together, G1+S+G2 make up interphase.
Concept context
Mitosis and meiosis: how cells divide for growth, repair, and reproduction.