Question

Decision of ${G_0}$-phase occurs
A. Towards the end of ${G_1}$-phase
B. Before the middle of ${G_1}$-phase
C. At the end of telophase
D. Towards the end of cytokinesis

Answer 1

The ${G_0}$-phase is a temporary phase where all cell activities related to division cease. It usually occurs at the onset of unfavourable conditions. After this, the cell divides only when it is needed or the favourable conditions are back. The ${G_0}$-phase can be temporary or even permanent.

Complete answer: The cell takes the decision to enter the ${G_0}$-phase just before the middle of the ${G_1}$-phase. ${G_1}$-phase is also called the first gap phase, or the post-mitotic phase, or the pre-synthetic phase. During the ${G_1}$-phase, the RNA and the protein synthesis becomes fast. It is at this time that the cell has to make the decision whether it wants to divide further or become inactive. This point is known as the transition point. The transition point occurs from the beginning of the ${G_1}$-phase to a point somewhere at the ${G_1}$-phase. The cell has to make up its decision during this slot of time only. The ${G_0}$ cells can have a temporary or a permanent ${G_0}$-phase. Moreover, antiphase is that phase where the cell becomes bound to divide and it cannot re-enter back into the ${G_0}$-phase or ${G_1}$-phase.
Hence, the correct answer is option B.

Note: The synthesis of RNAs like mRNA, rRNA, and tRNA becomes fast during the ${G_1}$-phase along with the protein synthesis. During this time most of the cell organelles get duplicated. The synthesis of the ATP and nucleotides increases. Due to these metabolic changes the size of the cell increases gradually.