During which phase does DNA synthesis occur?
A.
G1
B.
G2
C.
M.
D.
S
The correct answer and Explanation is :
The correct answer is D. S phase.
Explanation
DNA synthesis occurs during the S phase, or Synthesis phase, of the cell cycle. The cell cycle is divided into several phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis). Each phase has specific functions that contribute to the cell’s preparation for division.
- G1 Phase: In this initial phase, the cell grows and synthesizes proteins necessary for DNA replication. It also performs normal metabolic functions. At the end of G1, the cell assesses whether it is ready to proceed to the S phase based on various internal and external signals.
- S Phase: This is the critical phase where DNA replication occurs. Each chromosome is duplicated, resulting in two sister chromatids for each chromosome. This ensures that when the cell divides during mitosis, each daughter cell will receive an identical set of chromosomes. The replication process involves several key enzymes, including DNA polymerase, which synthesizes new strands of DNA complementary to the original strands.
- G2 Phase: Following DNA synthesis, the cell enters the G2 phase, where it continues to grow and produce proteins, preparing for mitosis. The cell checks the duplicated DNA for any errors, ensuring that it is ready for division. If any damage or issues are detected, the cell cycle may halt until repairs are made.
- M Phase: The M phase encompasses mitosis and cytokinesis, where the cell divides into two daughter cells. At this point, the DNA is already replicated, and the focus shifts to the separation of the sister chromatids.
In summary, the S phase is essential for ensuring that each daughter cell inherits a complete set of genetic material, making it a vital step in the overall process of cellular replication and division.