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 to thousands of chromosomes, each present in many copies.[1][2] 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.

See alsoEdit


  1. ^ Mochizuki K (2010-07-15). "DNA rearrangements directed by non-coding RNAs in ciliates". Wiley Interdisciplinary Reviews: RNA. 1 (3): 376–87. doi:10.1002/wrna.34. PMC 3746294. PMID 21956937.
  2. ^ Pevsner J (August 2015). Bioinformatics and Functional Genomics. John Wiley & Sons. ISBN 978-1-118-58176-6.