Question

In a diploid cell, at which stage of cell cycle, the amount of DNA is doubled?

(a) G₁ and G₂ phase 

(b) G₀ phase

(c) S, G₂ and M phase 

(d) S phase

Answer 1

The correct option is: (d) S phase

Explanation:

Cell cycle is a series of cyclic changes through which a cell passes during its growth and divisions. In the cell cycle, the resting stage or interphase can be divided into three periods.

(i) The post mitotic gap phase (G₁) takes place at the end of one cell division. RNA and protein synthesis occurs. 

(ii) During the synthetic phase (S), DNA is replicated and the DNA content of the nucleus is doubled. 

(iii) During the pre-mitotic gap phase (G₁) synthesis of RNA and protein continues, but DNA synthesis stops. The duration of the S phase, the G₂ phase and mitosis is generally constant in most cell types.