Question

Cell would normally proceed to mitosis without interruption
A. Once it has entered the S phase
B. Once it has entered the${G_2}$phase
C. At any time during cell division activity
D. None of these

Answer 1

Mitosis is a stage of the cell cycle in which replicated chromosomes are split into two nuclei. When a cell divides, it produces genetically identical cells with the same number of chromosomes. As a result, mitosis is often referred to as equational division. Mitosis is usually preceded by the S stage of interphase and followed by telophase and cytokinesis, which divides one cell’s cytoplasm, organelles, and cell membrane into two new cells with almost equal amounts of all these cellular components.

Complete answer:
Option A Once it has entered the S phase: The S phase, also known as Synthesis Phase, is the stage of the cell cycle during which DNA is copied, and it occurs between ${G_1}$ and ${G_2}$. The mechanisms that occur during S-phase are strictly regulated and widely conserved, as correct genome duplication is vital to proper cell division. Once the cell has entered the S phase, it would normally proceed to mitosis. Hence option A is the correct answer.
Option B Once it has entered the ${G_2}$ phase: The third subphase of interphase in the cell cycle, directly preceding mitosis, is known as ${G_2}$. It occurs after the S phase, during which the cell's DNA is duplicated, has completed successfully. With the commencement of prophase, the first phase of mitosis, the cell's chromatin condenses into chromosomes, ${G_2}$ phase comes to an end. Hence option B is not correct.
Option C At any time during cell division activity: A parent cell divides into two or more daughter cells in the process of cell division. Mitosis is a cell cycle stage in which duplicated chromosomes are separated into two new nuclei. When cells enter the S phase, they generally proceed to mitosis without interruption. Hence option C is not correct.
Option D None of these: Since option A is already the correct answer, option D is wrong.

Hence, option A. Once it has entered the S phase is the correct answer.

Note:
Mitosis is a process that happens solely in eukaryotic cells. Prokaryotic cells, which do not have a nucleus, divide through a process known as binary fission. Mitosis occurs in a variety of ways in different organisms. Animal cells, for example, go through an "open" mitosis in which the nuclear envelope breaks down before the chromosomes separate, whereas fungi go through a "closed" mitosis in which the chromosomes divide within a cell nucleus that is still intact.