Interphase - Stages of Interphase

Stages of Interphase

There are three stages of interphase, with each phase ending when a cellular checkpoint checks the accuracy of the stage's completion before proceeding to the next. The stages of interphase are:

• G₁ (Gap 1), in which the cell grows and functions normally. During this time, much protein synthesis occurs and the cell grows (to about double its original size) - more organelles are produced, increasing the volume of the cytoplasm. If the cell is not to divide again, it will remain in this phase.

• Synthesis (S), in which the cell duplicates its DNA (via semiconservative replication). This is also known as the Swanson phase.

• G₂ (Gap 2), in which the cell resumes its growth in preparation for division.

• In addition, some cells that do not divide often or ever, enter a stage called G₀ (Gap zero), which is either a stage separate from interphase or an extended G₁.

The duration of time spent in interphase and in each stage of interphase is variable and depends on both the type of cell and the species of organism it belongs to. Most cells of adult mammals spend about 20 hours in interphase, this accounts for about 90% of the total time involved in cell division. Interphase includes G1, S, and G2 phases. Mitosis and cytokinesis however, are separate from interphase.