Optometry Admission Test (OAT) Practice

What is primarily synthesized in the S stage of cell division?

1. Proteins

2. RNA

3. DNA

4. Lipids

The correct answer is: DNA

During the S stage, which stands for Synthesis phase, of the cell cycle, the primary activity is the replication of DNA. This is a crucial process that ensures that when a cell divides, each daughter cell receives an identical set of chromosomes. In this stage, the cell synthesizes an exact copy of its DNA so that there are two complete sets by the time cell division occurs in the M phase (Mitosis). The replication process involves unwinding the double helix structure of DNA and synthesizing new strands using existing strands as templates. This ensures genetic material is accurately passed on during cell division. While proteins, RNA, and lipids are also vital components synthesized during different phases of the cell cycle, they do not undergo primary synthesis in the S phase. Protein synthesis predominantly occurs during the G1 (Gap 1) and G2 (Gap 2) phases, RNA is synthesized throughout the cell cycle but is particularly prominent in transcription for protein synthesis, and lipid synthesis is often associated with cell membrane formation and energy storage, typically occurring in G1 and G2 phases as well. Therefore, the correct focus for the S phase specifically highlights the crucial process of DNA synthesis.