Question

Which of the following phases correspond to the interval between mitosis and the initiation of DNA replication?
A) S phase
B) ${G_1}$ phase
C) ${G_1}$ phase
D) M phase

Answer 1

Cell cycle consists of two stages. They are interphase and M phase. M phase is also called a mitotic phase in which actual cell division takes place. During interphase, the cell prepares itself for the cell division.

Complete answer:
We can divide interphase into three stages. They are ${G_1}$ phase, S phase and ${G_2}$ phase. After the ${G_2}$ phase, the cell enters the mitotic phase in which cell division occurs.

${G_1}$ phase is also called the Gap 1 phase. It is the interval between previous mitosis and S phase. During this phase, the cell prepares itself for DNA replication. Cell increases in size and prepares some proteins required for cell division. After the ${G_1}$ phase, the cell enters S phase.

During S phase, the DNA replication takes place. As new DNA is synthesised in this stage, it is called the synthesis phase. It occurs between ${G_1}$ and ${G_2}$ phase. Amount of DNA is doubled but no change in chromosome number is seen.

In ${G_2}$ phase, synthesis of proteins occurs. It is the phase between the S phase and the mitotic phase. It is the third phase of interphase. Know that cells can either enter the mitotic phase or remain in a quiescent phase which is called ${G_0}$ phase.

During M phase, actual cell division takes place. It includes both nuclear division followed by cytoplasmic division.

Hence the correct answer is option ‘C’.

Note: The process of nuclear division is called karyokinesis and cytoplasmic division is called cytokinesis. Know that in certain cases, cytokinesis doesn’t take place after nuclear division. It occurs in a multi nucleated condition in the cell.