Phases of Interphase | Cells | Don't Memorise

The cell cycle has two major phases: interphase and M phase. Interphase is longer because it involves preparation for cell division, which occurs in the M phase. This video will explore both phases in detail, starting with interphase and its sub-stages.

The G1 phase is the first stage of interphase, occurring between the M phase of the previous cycle and the S phase of the current cycle. In this preparatory phase, the cell is metabolically active, grows in size, and all organelles duplicate. Building blocks needed for later stages are synthesized, but DNA replication does not occur.

The S phase is where DNA replication occurs, duplicating the genetic material in the nucleus. Additionally, the centrosome, a bundle of threads containing centrioles important for separating sister chromatids during cell division, also duplicates in this phase. This ensures the cell has all necessary components for division.

The G2 phase involves further cell growth, enlargement, and the production of more proteins and organelles. Its most crucial function is to prepare the cell for mitosis and the actual cell division in the M phase, ensuring the cell is ready for the next stage of the cycle.

The G0 phase is an intermediate stage that cells may enter after the M phase and before the G1 phase, depending on intrinsic and extrinsic factors like resource availability. It was classically considered a resting phase where the cell is metabolically active but does not divide. Recent studies categorize it into a 'quiescent stage' if cells can reversibly return to G1, or a 'senescent stage' if they irreversibly stop dividing.

With all the preparatory stages of interphase complete, the cell is now ready to enter the M phase, which involves either mitosis or meiosis, depending on the cell type. The M phase itself has different stages, which will be discussed in future videos.