Interphaseis the active portion of thecell cyclethat includes theG1,S,andG2phases, where the cellgrows,replicates its DNA,and prepares formitosis,respectively. Interphase was formerly called the "resting phase,"but the cell in interphase is not simplydormant.Calling it so would be misleading since a cell in interphase is very busysynthesizing proteins,transcribing DNA into RNA,engulfing extracellular material,andprocessing signals,to name just a few activities. The cell is quiescent only inG0.Interphase is the phase of thecell cyclein which a typicalcellspends most of its life. Interphase is the "daily living" ormetabolicphase of the cell, in which the cell obtainsnutrientsandmetabolizesthem, grows, replicates its DNA in preparation formitosis,and conducts other "normal" cell functions.[1]
A common misconception is that interphase is the first stage ofmitosis,but since mitosis is the division of thenucleus,prophaseis actually the first stage.[2]
In interphase, the cell gets itself ready formitosisormeiosis.Somatic cells,or normaldiploidcells of the body, go through mitosis in order to reproduce themselves through cell division, whereas diploidgerm cells(i.e., primaryspermatocytesand primaryoocytes) go throughmeiosisin order to create haploidgametes(i.e.,spermandova) for the purpose of sexual reproduction.
Stages of interphase
editThere are three stages of cellular interphase, with each phase ending when acellular checkpointchecks 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, a high amount ofprotein synthesisoccurs and the cell grows (to about double its original size) – moreorganellesare produced and the volume of thecytoplasmincreases. If the cell is not to divide again, it will enterG0.[3]
- Synthesis(S), in which the cell synthesizes its DNA and the amount of DNA is doubled but the number of chromosomes remains constant (viasemiconservative replication).
- G2(Gap 2), in which the cell resumes its growth in preparation for division. The cell continues to grow until mitosis begins. In plants, chloroplasts divide during G2.
- In addition, some cells that do not divide often or ever, enter a stage calledG0(Gap zero), which is either a stage separate from interphase or an extendedG1.
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 adultmammalsspend about 24 hours in interphase; this accounts for about 90%-96% of the total time involved in cell division.[4] Interphase includes G1, S, and G2 phases.Mitosisandcytokinesis,however, are separate from interphase.
DNA double-strand breaks can berepairedduring interphase by two principal processes.[5]The first process,non-homologous end joining(NHEJ), can join the two broken ends of DNA in theG1,SandG2phases of interphase. The second process,homologous recombinationalrepair (HRR), is more accurate than NHEJ in repairing double-strand breaks. However HRR is only active during the S and G2 phases of interphase whenDNA replicationis either partially or fully accomplished, since HRR requires two adjacenthomologous chromosomes.
Interphase within sequences of cellular processes
editInterphase and the cell cycle
editWhen G2is 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 resultingdaughter cellsre-enter G1of interphase.
In thecell cycle,interphase is preceded bytelophaseandcytokinesisof theM phase.In alternative fashion, interphase is sometimes interrupted byG0phase,which, in some circumstances, may then end and be followed by the remaining stages of interphase. After the successful completion of theG2checkpoint,the final checkpoint in interphase, the cell proceeds toprophase,or in plants topreprophase,which is the first stage of mitosis.
G0phase is viewed as either an extended G1phase where the cell is neither dividing nor preparing to divide, or as a distinctquiescentstage which occurs outside of the cell cycle.[6]
Interphase and other cellular processes
editIngameteproduction, interphase is succeeded bymeiosis.Inprogrammed cell death,interphase is followed or preempted byapoptosis.
See also
editInterphase (Materials)
editThe transition region between two materials. For example between thefibreand matrix of acomposite material.
References
edit- ^Marieb E (2000).Essentials of human anatomy and physiology.San Francisco: Benjamin Cummings.ISBN978-0805349405.
- ^"The Cell Cycle & Mitosis Tutorial".The Biology Project – Cell Biology.University of Arizona.
- ^Cummings MR (2014).Human Heredity: Principles and Issues(10th ed.). Belmont, CA: Brooks/Cole. pp.28–29.
- ^Mader SS (2007).Biology(9th ed.). Boston, MA, USA: McGraw Hill Higher Education.ISBN978-0-07-325839-3.
- ^Shibata A. Regulation of repair pathway choice at two-ended DNA double-strand breaks. Mutat Res. 2017 Oct;803-805:51-55. doi: 10.1016/j.mrfmmm.2017.07.011. Epub 2017 Jul 29. Review. PMID 28781144
- ^Cram E."Re: Are the cells in the G0 (g zero) phase of mitosis really suspended?".MadScience Network.Molecular and Cellular Biology, University of California, Berkeley. 1999.