Question

Given below is a schematic breakup of the phases or stages of the cell cycle.

Which one of the following is the correct indication of the stage/phase in the cell cycle?
a) C - Karyokinesis
b) D - Synthetic phase
c) A - Cytokinesis
d) B - Metaphase

Answer 1

Cell cycle is a duration of time in which the cell undergoes division and replication of its content. It leads to the multiplication of the number of cells that were originally present. The cell has to pass different stages in which each stage has its own significance.

Complete answer:
In mitosis there are substages which include prophase, prometaphase, metaphase, anaphase and telophase. The first three phases are part of karyokinesis in which only division of the nuclear material takes place. And the telophase leads to the cytokinesis of the cell which means that cell gets divided into daughter cells in this phase. Metaphase is the phase in which the chromosomes line up at the metaphase plate or the equatorial plate. They are held at that plate by the force of a mitotic spindle. The spindle attaches itself to the chromosome and gets ready for the sister chromatid to divide.

Additional information:
- Karyokinesis is the process in which the nuclear component of the cell divides. This stage starts with the disappearance of the nuclear envelope and appearance of the spindle bundle followed by the arrangement of chromosomes at the equatorial plate. They are then separated by the force of the spindle fibre attached to them and are pulled apart to the either poles. This condition marks the ending of the karyokinesis and beginning of the cytokinesis.
- Cytokinesis is the process in which the mother cell divides to form the daughter cell. It starts with the formation of a groove on the cell wall followed by the appearance of the nuclear membrane or envelope. The phase ends with the formation of two daughter nuclei.
- S phase is known as the synthesis phase. It is the phase in which the replication of DNA takes place. It plays a crucial role in the cell cycle as replication of DNA is necessary for the cell division.
So, the answer is ‘d) B-metaphase’.

Note: S phase is not known as the synthetic phase instead it is known as synthesis phase. This confusion may lead to choosing the wrong option. Also, karyokinesis occurs before the cytokinesis and not the other way round. After successful karyokinesis comes the stage of cytokinesis.