出典:Wiktionary
出典:『Wiktionary』 (2016/04/27 13:08 UTC 版)
macronucleus (複数形 macronuclei)
出典:Wikipedia
出典:『Wikipedia』 (2011/05/26 19:52 UTC 版)
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, the everyday tasks, 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 a mystery.