University of Central Florida (UCF) PCB3023 Molecular Cell Biology Practice Exam 4

During the G1 phase of the cell cycle, cells primarily focus on cell growth, preparation for DNA synthesis, and maintaining cellular functions, rather than directly destroying cyclins. The correct answer relates to the important processes occurring during this phase.

During G1, the cell grows in size, synthesizes various proteins, and produces organelles. It also accumulates the necessary building blocks and energy reserves required for DNA replication, which occurs in the subsequent S phase. Additionally, the cell assesses its internal and external environment to ensure it is ready to proceed with division.

Repairing DNA damage, while a crucial function of the cell, is particularly emphasized during the G1 phase if any cellular damage is detected. This ensures the integrity of the genetic material before duplication occurs. However, the act of separating sister chromatids is not a function of G1 but rather takes place during mitosis.

While cyclins do play a role in regulating the cell cycle by partnering with cyclin-dependent kinases (CDKs) to signal transitions between phases, the destruction of cyclins typically occurs later in the cycle after they have served their regulatory purpose. Hence, G1 is not characterized by this process, making that choice incorrect.