• synonyms


[mahy-kroh-noo-klee-uh s, -nyoo-]
noun, plural mi·cro·nu·cle·i [mahy-kroh-noo-klee-ahy, -nyoo-] /ˌmaɪ kroʊˈnu kliˌaɪ, -ˈnyu-/. Biology.
  1. the smaller of the two types of nuclei occurring in ciliate protozoans.
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Compare macronucleus.

Origin of micronucleus

First recorded in 1890–95; micro- + nucleus
Related formsmi·cro·nu·cle·ar, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for micronucleus

Historical Examples of micronucleus

  • In the latter case it is often called the paranucleus or micronucleus.

    A Guide for the Study of Animals

    Worrallo Whitney

  • The macronucleus is spherical and has one micronucleus attached.

  • Both the small nucleus (micronucleus) and the large nucleus (macronucleus) divide at each division of the body.

  • The macronucleus is usually dorsal, elliptical, and cleft, with one micronucleus attached.

  • The macronucleus is central, spherical in form, and bears a single minute micronucleus.

British Dictionary definitions for micronucleus


noun plural -clei (-klɪˌaɪ) or -cleuses
  1. the smaller of two nuclei in ciliated protozoans, involved in reproductionCompare macronucleus
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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

micronucleus in Medicine


  1. A minute nucleus.
  2. The smaller of two nuclei in ciliate protozoans that contains genetic material and functions in reproduction.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.