Question

Name and explain the various stages of the cell cycle.

Answer 1

Stages of the cell cycle:

• Non-dividing interphase
• Dividing mitotic phase or M phase

Interphase:

In interphase, cells grow in size and volume and prepare for the next cell division.

It is divided into three phases:

• First growth phase (G₁):RNA and proteins are synthesised, and the volume of the cytoplasm increases.
• Synthesis phase (S):DNA is synthesised and chromosomes are duplicated.
• Second growth phase (G₂):RNA and proteins continue to be synthesised.

Mitosis:

Mitosis is the division of somatic cells in which two identical daughter cells are produced by the division of one parent cell.

It consists of the following phases:

• Karyokinesis: It is the division of the nucleus during cell division.
• Cytokinesis: It is the division of the cytoplasm during cell division.

Karyokinesis:

It occurs in four phases:

• Prophase: During prophase, chromatinfibres condense and thick chromosomes are visible. The nucleolus and nuclear membrane disappear. A pair of centrioles duplicates. The spindle apparatus starts forming.
• Metaphase: Chromosomes are arranged on the metaphase plate or equatorial plane.
• Anaphase: The centromere divides, and the sister chromatids separate from each other. Spindlefibres contract and pull chromatids towards opposite poles.
• Telophase: Spindle apparatus disappears. Chromosomes become thin and turn into chromatinfibres. Nuclear membranes and nucleoli reappear.

Cytokinesis:

• The furrow continues to deepen in the cell, and it finally divides the cytoplasm forming two new daughter cells.
• In plant cells, a cell plate appears at the equatorial plane.