Cell Cycle and Cell Division
All organisms start their life from a single cell and grow by the addition of new cells. The new cells arise by the division of pre-existing cells. This idea was suggested by Rudolf Virchow in 1858 in a particular statement ‘Omnis Cellula e Cellula’, means ‘every cell produces from a cell. This states that the continuity of life depends on cell reproduction or cell division.
Cell Cycle
Cell Cycle was introduced by Howard and Pele in 1953. It is defined as the series of events hy which a cell duplicates its genome and synthesises other cell components and then divides into two daughter cells
Phases of Cell Cycle
Cell cycle occurs in the following two phases
1.Interphase (undividing phase)
2. M Phase or Mitosis Phase (dividing phase)
1. Interphase
It represents the phase between two successive M phases. It constitutes or lasts for more than 95% of the whole duration of cell cycle. Though it is called the resting phase, but it is the time during which the newly formed cells prepare themselves for division i.e., to undergo both growth and DNA replication in an orderly manner.
Interphase involves three phases as given below
G4 Phase
First gap phase, represents time between mitosis and initiation of DNA replication, cells are metabolically active, grow continuously, produce carbohydrates, lipids, proteins, etc, DNA content remains the same, replication do not occur.
S Phase
Synthesis phase, DNA replication occurs, DNA content doubles from 2C to 4c
G2 Phase