InterphaseInterphase is the phase of the cell cycle in which a typical cell spends most of its life. During interphase, the cell copies its DNA in preparation for mitosis. Interphase is the 'daily living' or metabolic phase of the cell, in which the cell obtains nutrients and metabolizes them, grows, reads its DNA, and conducts other "normal" cell functions. This phase was formerly called the resting phase. However, interphase does not describe a cell that is merely resting; rather, the cell is living and preparing for later cell division, so the name was changed. A common misconception is that interphase is the first stage of mitosis, but 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.
Stages of interphaseThere are three stages of cellular 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:
DNA double-strand breaks can be repaired during interphase by two principal processes. The first process, non-homologous end joining (NHEJ), can join the two broken ends of DNA in the G1, S and G2 phases of interphase. The second process, homologous recombinational repair (HRR), is more accurate than NHEJ in repairing double-strand breaks. However HRR is only active during the S and G2 phases of interphase when DNA replication is either partially or fully accomplished, since HRR requires two adjacent homologous chromosomes.
Interphase within sequences of cellular processes
Interphase and the cell cycleWhen G2 is 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 preceded by telophase and cytokinesis of the M phase. In alternative fashion, interphase is sometimes interrupted by G0 phase, which, in some circumstances, may 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.
G0 phase is viewed as either an extended G1 phase where the cell is neither dividing nor preparing to divide, or as a distinct quiescent stage which occurs outside of the cell cycle.