Cell Cycle:
The cell cycle is an orderly sequence of events or a set of stages by which a cell duplicates its genome, synthesises the other constituents (important for the cell) of the cell and eventually divides into two daughter cells.
Interphase:
It is the period between the end of one cell division to the beginning of the next cell division, i.e., (between two successive M- phase).
During this phase, the cell prepares itself for both cell growth and DNA replication in an orderly manner. So, it is also known as the preparation phase. It lasts for about 90-96%, i.e., more than 95% of the total duration of the cell cycle. In a cell cycle of human cell, only about one hour is taken by the dividing phase out of 24 hours duration of one cell cycle. Interphase is further divided into following three substages on the basis of various synthetic activities
i. G₁(Gap-1)-phase
It corresponds to the duration between the mitosis (M-phase) and initiation of replication of DNA. The cell becomes metabolically very active during this period. It grows continuously and prepares itself for DNA replication. Thus synthesising enzymes and proteins needed for this process.
ii. S (Synthesis)-phase
It is known to be the phase in which actual synthesis or replication of DNA takes place. The overall amount of DNA doubles per cell, but no increase in chromosome number takes place during this phase. If the initial amount of DNA is 2C, it will become 4C.
In the case of an animal cell, during S-phase DNA replication begins inside the nucleus while the duplication of centrioles takes place in the cytoplasm.
iii. G2 (Gap-2)-phase This phase is also called post-synthetic or pre-mitotic phase. During this stage, the synthesis of DNA stops and proteins required for mitosis are being synthesised while the growth of cell continues. It prepares the cell to undergo division.