cell cycle - interphase

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 cell division. In preparation for cell division, it increases its 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. Interphase does not describe a cell that is merely resting but is rather an active preparation for cell division. 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.[1]

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.

2013-5-19 21:31:29

Posted by DoctorZ | 阅读全文 | 回复(1) | 引用通告 | 编辑

Re:cell cycle - 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, a high amount of 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.[2] Interphase includes G1, S, and G2 phases. Mitosis and cytokinesis however, are separate from interphase.

2013-5-19 21:33:25

Posted by doctorzhang | 个人主页 | 引用 | 返回 | 删除 | 回复


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