Answer on Cell Biology Question for Sanjukta Ghosh
What are the different checkpoints in cell cycle? I'm having trouble sorting the different checkpoints in cell cycle.I have suggested wikipedia it says there are three checkpoints; restriction point, G2-M DNA damage checkpoint and Spindle attachment checkpoint. But again 'Molecular Biology of the Cell' by Alberts and Johnson has mentioned of two DNA damage checkpoints , one at G1 and the other at G2. There's no book saying what exactly are the different checkpoints in cell cycle. Please assist. I would like to know the name of a book that has the different checkpoints mentioned.
A good description of checkpoints is present in Sylvia Mader "Biology" (2010). It states that there are three checkpoints: G1 (restriction), G2 (DNA damage) and M (spindle fiber). G1 occurs at the G1 stage of interphase. As the cell spends most of the time at this stage, there is high probability for mutations due to action of negative factors of the environment. Thus, the cell checks for DNA mutations at the G1 stage, if it is going to proceed with the cell cycle. The second checkpoint occurs at G2 stage to check, if DNA has replicated properly. The third checkpoint occurs during the metaphase of mitosis. It checks for the proper attachment of spindle fibers to chromosomes. If they have not attached yet, and cell proceeds to anaphase, there is high chance for chromosome number abnormalities as they will be randomly distributed between the daughter cells. Thus, one cell will get extra chromosomes while another will lack some. Only when cell ensures that chromosomes are properly attached to the spindle fibers, it proceeds with meiosis and chromatids move to the different daughter cells.
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