Macronucleus

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.

Levels of organization	Unicellular Monadoid Amoeboid Coccoid Colonial s.s. Colonial flagellated Tetrasporal/capsal/palmelloid Sarcinoid Coenobial Filamentous/trichal/hyphal Parenchymatous Pseudoparenchymatous/plektenchymatic Membranous/thalloid/foliaceous Multinucleated Syncytial Coenocytic Siphonous Siphonocladous Multicellular s.s./tissular/histonal

Cell surface structures	Simple cell membrane Mucilage Scale Frustule Cell wall Lorica Skeleton Test Theca Periplast/pellicle

Locomotion	Flagellum Cilia Pseudopodia Gliding motility

Mitochondria	Hydrogenosome Mitosome

Nucleus	Nucleomorph Multinucleate cells Plasmodium Dikaryon Heterokaryon Mitosis in protists Open Closed Orthomitosis Pleuromitosis Meiosis in protists Gametic Zygotic Sporic

Other	Cyst Cytostome Fimbriae Extrusome Contractile vacuole Eyespot apparatus Pyrenoid Axostyle Mastigont system

Ecology and
physiology

Microbial ecology
- Microbial biogeography
- Baas-Becking hypothesis
Development/Reproduction
- Life cycles
- Fertilization
Nutrition: Autotrophy
- Phototrophy
Heterotrophy
- Phagotrophy
- Osmotrophy
- Saprotrophy
- Parasitism
  - Biotrophy
  - Necrotrophy
Mixotrophy
Auxotrophy

This article is issued from Wikipedia - version of the 10/4/2014. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.

Macronucleus

See also