12. A cell has increased in size and is preparing to divide. Before division can occur, the DNA must be replicated. In which stage of the cell cycle is DNA replicated?
Answer: A
DNA is replicated during the Synthesis phase of the cell cycle.
During the Synthesis phase, commonly referred to as the S phase, the cell replicates its DNA in preparation for cell division. This ensures that each daughter cell will receive an identical set of chromosomes.
A) Synthesis
Option A is correct because the Synthesis phase is specifically designated for the replication of DNA, where the entire genome is duplicated to ensure that both daughter cells have the necessary genetic material.
B) G1
Option B is incorrect as G1, or Gap 1, is the phase where the cell grows and carries out normal functions, but DNA replication does not occur during this stage. It is primarily focused on preparing the cell for the S phase.
C) G2
Option C is also incorrect because G2, or Gap 2, is the phase that follows DNA replication. During G2, the cell continues to grow and prepares for mitosis, but DNA replication has already taken place in the S phase.
D) Cytokinesis
Option D is incorrect as Cytokinesis is the process of cytoplasmic division that occurs after mitosis, not a phase where DNA replication happens. By this point, the DNA has already been replicated during the S phase.
Conclusion
The Synthesis phase is definitively the stage of the cell cycle where DNA replication occurs, ensuring that each daughter cell receives a complete set of chromosomes. All other options describe different phases of the cell cycle where DNA replication does not take place, thereby confirming that A is the only correct answer.