Wiktionary
n. (context biology English) The larger of the two nuclei present in ciliate protozoans; it controls the nonreproductive functions of the cell.
Wikipedia
A macronucleus (formerly also meganucleus) is the larger type of nucleus in ciliates. Macronuclei are polyploid and undergo direct division without mitosis. It controls the non-reproductive cell functions, such as metabolism. During conjugation, the macronucleus disintegrates, and a new macronucleus is formed by karyogamy of the micronuclei. The macronucleus contains hundreds of chromosomes, each present in many copies. The macronucleus lacks a mechanism to precisely partition this complex genome equally during nuclear division; thus, how the cell manages to maintain a balanced genome after generations of divisions is unknown.
Usage examples of "macronucleus".
There are three different sets of self-duplicating nuclei, with the DNA in each set serving different purposes: a large macronucleus, governing the events in regeneration after injury, a set of eight or more micronuclei containing the parts of the genome needed for reproduction, and great numbers of tiny nuclei from which the cilia arise.
Have recorded over a dozen specimens in which the macronucleus is unquestionably double.