Interphase

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 Interphase is the stage in The Cell Cycle where cells are preparing for Cell Division. It is used as a checkpoint to make sure that the cell is ready to proceed into mitosis or meiosis. There are 3 phases of Interphase - G1,G2 and the S-Phase. Within the G1 Phase there is G0 or quiescent stage, which takes place outside the Cell Cycle. During Interphase , the cell is still actively expressing its genes and the DNA is being replicated during interphase, so that the cell can enter M Phase[1].

Contents

G1 Phase

G1 (G stands for Gap) phase is the intermediate of interphase between the end of cell division and the beginning of DNA replication in the S phase. It comprises of the cell making a variety of proteins requires for DNA replication[2]. G1 is a review of cellular conditions to ensure they are appropriate for DNA replication. If it is not appropriate cells can enter a phase called G0 phase, a pause in G1 until the cell is ready to enter S phase, where cells are said to be quiescent. Cells in this state may eventually re-enter G1 or may perhaps die. This is to ensure that damaged or defective DNA sequences are not passed on to daughter cells[3].

S Phase

This is the phase when DNA, packaged into chromosomes, is replicated, meaning each cell has the same genetic makeup. Therefore each chromosome now consists of two sister chromatids. Chromosomes therefore double their number of chromatids but retain a diploid nuclei. Also, cell growth continues through S phase, as well as the rate of synthesis of a number of proteins and enzymes involved in DNA synthesis[4].

G2 Phase

G2 phase is the final phase of interphase, in which the cell synthesises a variety of proteins. Microtubules, a vital protein in mitosis, is also synthesised. G2 is also the final growth before M phase, a checkpoint of sorts to ensure intracellular components have been properly replicated.

References

  1. Alberts B., Bray D., Hopkin K.,Johnson A., Lewis J., Raff M., Roberts K and Walter P. (2003) essential cell biology 2nd edition (p182), New York: Garland Science
  2. Cyberbridge Interphase. Available at : http://cyberbridge.mcb.harvard.edu/mitosis_4.html
  3. MadSci Network (1999) Are the cells in the G0 (g zero phase of mitosis really suspended? Avaiable at: http://www.madsci.org/posts/archives/nov99/942335648.Cb.r.html
  4. Spark notes, Components of the cell cycle. Available at: http://www.sparknotes.com/biology/cellreproduction/cellcycle/section1.html
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