Cell Cycle - Research Article from Macmillan Science Library: Plant Sciences

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The Phases of the Cell Cycle

The cell cycle is commonly described as having four phases: M (mitosis), Gap 1 (postmitotic interphase), S-phase (period of DNA synthesis), and Gap 2 (postsynthetic interphase). Gaps 1 and 2 were initially thought to be resting stages between mitosis and S-phase. This description is a misnomer because numerous genes regulate cell growth in these phases. Appropriately, these terms became abbreviated to G1 and G2. Moreover, networks of cell cycle gene products constitute molecular checkpoints that in G1 determine whether a cell is competent to replicate its chromosomes during S-phase, and that in G2 sense whether the cell is ready to partition its chromatids during mitosis. Uniquely in plant cells, in late G2 an array of microtubules known as the preprophase band appears and chromosomes separate in a plane perpendicular to it.

Only in mitosis do chromosomes become visible by light microscopy; each one appears as two...

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This section contains 1,014 words
(approx. 4 pages at 300 words per page)
Buy the Cell Cycle Encyclopedia Article
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Macmillan Science Library: Plant Sciences
Cell Cycle from Macmillan Science Library: Plant Sciences. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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