Question

In ‘S’ phase of cell cycle
A. Amount of DNA remains same in each
B. Chromosome number is increased
C. Amount of DNA is reduced to half in each cell
D. Amount of DNA doubles in each cell

Answer 1

Hint: The S phase is one of the stages of mitosis. Mitosis is an equational division, which means that the number of chromosomes in the daughter cells is the same as that in the parent cell. During the S or synthesis phase, the cell prepares itself before undergoing actual cell division.

Complete answer:
In the ‘S’ phase of the cell cycle, the amount of DNA doubles in each cell.
Mitosis is divided into two main phases – the Interphase and M phase.
The M phase refers to the actual cell division. Interphase is the preparatory phase between two cell divisions.

The interphase is divided into:
• G1 phase
• S phase
• G2 phase

During the G1 phase (Gap1), the cell does not replicate its DNA, however, it is metabolically active. From the G1 phase, the cell enters the S phase. In this phase, DNA gets synthesised and its amount gets doubled in each cell. After this, the cell enters the G2 phase, in which the proteins needed for mitosis are synthesised in the cells. Once all the phases of interphase are over, the cell becomes ready to enter the M phase – the actual process of the cell division. At the end of the M phase, one cell divides to form two daughter cells.

Hence, the correct answer is option (D).

Note: During the S phase, the amount of DNA gets doubled in each cell. The number of chromosomes remains the same. The S phase also functions as a checkpoint for the cell. The DNA of the cell is checked for abnormalities and if the damage is detected, the cell cycle gets arrested or delayed.