Advanced Placement (AP) Biology Practice Exam

What characterizes the G1 phase of the cell cycle?

1. The cell prepares for mitosis

2. DNA synthesis occurs

3. The cell grows and prepares for DNA replication

4. The cell enters a resting phase

The correct answer is: The cell grows and prepares for DNA replication

The G1 phase of the cell cycle is characterized by the cell growing and preparing for DNA replication. During this phase, which stands for "Gap 1," the cell experiences various activities crucial for its growth and development, including synthesizing proteins, increasing organelle numbers, and accumulating nutrients necessary for DNA synthesis in the subsequent S phase. In G1, the cell checks its environment and internal conditions to ensure readiness for replication; it does not yet replicate its DNA, which occurs exclusively in the S phase. This growth phase is critical as it sets up the cell to successfully undergo DNA replication and division later in the cycle. The processes and preparations that occur during G1 are vital for maintaining proper cellular function and ensuring that the cell can divide accurately and effectively in the later stages of the cell cycle.