Interphase of cell cycle is the resting phase of cell cycle. It is a stage of two successive M-phase. Although this is not an active cell division phase but the cell prepares itself for division in this phase. A specific time for the interphase is assigned for the DNA replication, whereas transcription (RNA synthesis) and translation (protein synthesis) occurs throughout the time. Depending upon the DNA replication time, the interphase is subdivided into 3 sub-stages e.g., G1 phase ( Gap Phase 1), S-phase ( Synthesis phase), G2 Phase ( Gap phase 2).
In a tissue where cells are actively dividing, G1 phase is shorter. G1 phase is responsible for plasmatic growth of the cell. Most of the cell organelle get duplicated in this phase and it's a time of prolific RNA synthesis and protein synthesis.Cell in this phase takes care of the dNTP synthesis and synthesis of proteins required in DNA replication.
Synthesis phase (S-phase) is assigned for DNA replication. In this phase the DNA amount doubles and chromosome number remains the same as the monad chromosomes transforms into dyad chromosomes. To stabilize new DNA, new histone proteins are also synthesized. Generally no cell organelle replicates during this phase except centriole.
Gap phase 2 (G2 phase) is the shortest sub-stage of interphase. This stage is assigned for the duplication of semi-autonomous cell organelles and golgi body. As transcription is almost negligible during M-phase all the necessary RNA are transcribed during G2. Spindle apparatus which is utmost necessary for chromosomal segregation during M-phase requires a lot of microtubules. The basic unit of microtubules, which is tubulin protein (α & β tubulin) get synthesised in this stage.
Transition from one cell-cycle stage to another is under a tight genetic regulation, and we are soon going to discuss that topic, so bugs, stay updated :)