The term interphase is derived from Latin word ‘inter’ which means ‘between’ and Greek word ‘phasis’ which means ‘appearance’. It occupies about 90% of the cell cycle and is a period of synthesis and growth, during which the cell roughly doubles in mass but without displaying obvious morphological changes.
Interphase as the name suggests, is the stage between two successive cell divisions during which the cell prepares itself for the process by growing in size and synthesizing new nucleic acids & proteins. Chromosomes appear as thread-like chromatin network.
Stages of Interphase
Interphase consists of the following three sub stages.
G1 or Gap-1 phase: This phase starts immediately after previous cell division. The cell grows in size and there is synthesis of new proteins and RNA which are needed for various metabolic activities of the cell. A non-dividing cell does not proceed beyond G1 phase and is said to be in G0 stage or cease phase.
S-or Synthetic Phase: During this phase there is synthesis of DNA. And each chromosome is now composed of two sister chromatids.
G2 or Gap-2 Phase: During this phase there is synthesis of proteins responsible for the formation of spindle fibres. Also the cell grows further in size.
In summary the following are the events which take place during interphase
- Synthesis of new proteins, DNA and RNA
- The nuclear envelope remains intact.
- The chromosomes occur in the form of diffused, long, coiled and unclearly visible chromatin fibres.
- Due to the accumulation of ribosomal RNA and proteins, the nucleolus reaches its maximum size.
- A daughter centrosome is originated near the existing centrosome and consequently an interphase cell has two centrosomes.
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