When would a cell most likely contain the most nucleotides?
A.
S
B.
G1
C.
M
D.
G2
The Correct answer and Explanation is:
The cell cycle is divided into several phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis). To determine when a cell would most likely contain the most nucleotides, it’s essential to understand what happens during each phase.
Correct Answer: A. S
Explanation:
- S Phase (Synthesis Phase): The S phase is characterized by DNA replication. During this phase, the cell synthesizes a complete copy of its DNA. As a result, the total amount of DNA—and thus the number of nucleotides—in the cell doubles. Each chromosome is replicated into two sister chromatids, each containing an identical copy of the DNA. Because nucleotides are the building blocks of DNA, and the cell’s DNA content is doubled during this phase, the cell contains the highest number of nucleotides in the S phase.
- G1 Phase (Gap 1): In the G1 phase, the cell grows and carries out its normal metabolic functions. It prepares for DNA replication by producing the necessary proteins and organelles but does not replicate its DNA. Therefore, the number of nucleotides remains at the baseline level corresponding to a single set of chromosomes.
- G2 Phase (Gap 2): The G2 phase follows DNA replication and precedes mitosis. During G2, the cell continues to grow and prepare for cell division. It produces additional proteins and organelles but does not undergo DNA replication again. Hence, while the number of nucleotides is still higher than in G1, it does not reach the peak level seen during the S phase.
- M Phase (Mitosis): The M phase is when cell division occurs. The replicated chromosomes are separated into two daughter cells. The total amount of DNA—and thus the number of nucleotides—decreases as the cell divides. Each daughter cell receives a complete set of chromosomes, but the total nucleotide count per cell is lower compared to the S phase.
In summary, a cell contains the most nucleotides during the S phase due to the replication of its DNA, which doubles the nucleotide content.