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Question:
What is the catalyst that causes the mitotic process to start? I understand how DNA works, but what causes the cell to start dividing?



Replies:
Cells go through a cycle that has several distinct stages, called M (for mitosis), G1 (first Gap or Growth stage), S (for DNA synthesis) and G2 (second gap). The decision to divide is made during G1 stage, when the cell "senses" that its growth conditions or status is OK to divide. The real signal is not entirely clear yet; there are probably several such signals that get integrated together to make the decision. We are learning a lot about the machinery that then gets things moving; I can supply more details if you wish. Once the decision in G1 is made the rest of the cell cycle proceeds more or less like clockwork; 6-8 hours for DNA synthesis, a few hours in G2 (to get ready to divide), and an hour or so in Mitosis itself. Hope this answer is helpful; let me know if you want more details.

Steve J Triezenberg



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