Macronucleus

{{Short description|A type of nucleus in ciliates, involved in non-reproductive cell functions}}

{{Refimprove|date=November 2018}}

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 one is formed by karyogamy of the micronuclei.

Macronuclei contain hundreds to thousands of chromosomes, each present in many copies.{{cite journal | vauthors = Mochizuki K | title = DNA rearrangements directed by non-coding RNAs in ciliates | journal = Wiley Interdisciplinary Reviews: RNA | volume = 1 | issue = 3 | pages = 376–87 | date = 2010-07-15 | pmid = 21956937 | pmc = 3746294 | doi = 10.1002/wrna.34 }}{{Cite book |title=Bioinformatics and Functional Genomics |last=Pevsner |first=Jonathan | name-list-style = vanc | date = August 2015 | publisher=John Wiley & Sons |url=https://books.google.com/books?id=OaRjCgAAQBAJ&pg=PA900 |isbn=978-1-118-58176-6 |language=en}} There is no 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.