Cell cycle and cell division
The sequence of the events by which a cell duplicates its genome, synthesis the other constituents of the cell and eventually divides into to daughter cells is termed cell cycle.
In other words, Cell division cycle is a series of events which leads to duplication (Replication) of DNA and division of the cytoplasm to form daughter cells.
Actively dividing cells pass through a series of stages known collectively as the cell cycle.
Phases of cell cycle
Cell cycle pass through following different phases to undergo division.
- G1 phase (gap-1)
- S phase (synthesis)
- G2 phase (gap-2)
Interphase or Interkinesis
- Interphase is the phase between two successive cell division (end of one cell division to the beginning of next cell division).
- It is the longest phase in the cell cycle.
- Interphase looks dormant but it is metabolically active stage.
It is divided into 3 sub-stages which are: G1-phase, S-phase and G2-phase.
- G1-Phase or Gap-1 phase
- The cell grows in size due to active biosynthesis.
- Formation of structural and functional proteins.
- Synthesis of mRNA, tRNA and rRNA takes place.
- S-Phase or Synthetic phase: Duplication of genetic material takes place.
- Replication of DNA takes place.
- Synthesis of histone proteins takes place which covers DNA.
iii. G2-Phase or Gap-two phase or Second growth phase
- RNA and protein synthesiS.
- Centrioles get replicate (in case of animal cell)
- Synthesis of spindle proteins takes place.
M phase (Mitosis Phase)
In this phase partition of the nucleus (Karyokinesis) and genetic material as well as cytoplasm (Cytokinesis) occurs.
Types of cell division
There are two types of cell division:
In most cases “cell division” refer to mitosis which is the process of formation of two new daughter cells from parent cell while meiosis cell division is formation of four haploid cells from single diploid cells.