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Pronunciation: in-i'she-a'shun


  1. The first stage of tumor induction by a carcinogen; subtle alteration of cells by exposure to a carcinogenic agent so that they are likely to form a tumor on subsequent exposure to a promoting agent (promotion).
  2. Starting point of replication or translation in macromolecule biosynthesis.
  3. Start of chemical or enzymatic reaction.
  4. The first step in a chain reaction.
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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review Date: Sep 19, 2016.