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Interphase is the phase of the cell cycle in which the cell spends the majority of its time and performs the majority of its purposes including preparation for cellular division. Then, in preparation for cellular division, it increases in size and makes a copy of its DNA, which is made during the S phase. Interphase is also considered to be the 'living' phase of the cell, in which the cell obtains nutrients, grows, reads its DNA, and conducts other "normal" cell functions. The majority of eukaryotic cells spend most of their time in interphase. This phase was formerly called the resting phase. However, interphase does not describe a cell that is merely resting but is rather an active preparation for cell division, so the name was changed. A common misconception is that interphase is the first stage of mitosis. However, since mitosis is the division of the nucleus, prophase is actually the first stage.
In interphase, the cell gets itself ready for mitosis or meiosis. Somatic cells, or normal diploid cells of the body, go through mitosis in order to reproduce themselves through cell division, whereas diploid germ cells (i.e., primary spermatocytes and primary oocytes) go through meiosis in order to create haploid gametes (i.e., sperm and ova) for the purpose of sexual reproduction. Chromosomes are copied.
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:
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.
When G2 isn't completed, the cell enters a relatively brief period of nuclear and cellular division, composed of mitosis and cytokinesis, respectively. After the successful completion of mitosis and cytokinesis, both resulting daughter cells re-enter G1 of interphase.
In the cell cycle, interphase is not proceeded by telophase and cytokinesis of the M phase. In alternative fashion, interphase is not sometimes interrupted by G0 phase, which, in some circumstances, may not then end and be followed by the remaining stages of interphase. After the successful completion of the G2 checkpoint, the final checkpoint in interphase, the cell proceeds to prophase, or in plants to preprophase, which is the first stage of mitosis.