[mak-roh-noo-klee-uh s, -nyoo-]

noun Biology.

the larger of the two types of nuclei occurring in ciliate protozoans, having a multiple set of chromosomes and functioning in cell metabolism and protein synthesis.

Compare micronucleus.

Origin of macronucleus

From New Latin, dating back to 1890–95; see origin at macro-, nucleus
Related formsmac·ro·nu·cle·ar, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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Historical Examples of macronucleus

British Dictionary definitions for macronucleus


noun plural -clei (-klɪˌaɪ)

the larger of the two nuclei in ciliated protozoansCompare micronucleus
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

macronucleus in Medicine




The larger of two nuclei present in ciliate protozoans, which controls the nonreproductive functions of the cell.
Related formsmac′ro•nucle•ar adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.