The first gap period of the cell cycle.

The part of interphase of the cell cycle that precedes S phase.

The G1 phase is a period in the cell cycle during interphase, after cytokinesis and before the S phase. For many cells, this phase is the major period of cell growth during its lifespan. During this stage new organelles are being synthesized, so the cell requires both structural proteins and enzymes, resulting in great amount of protein synthesis.