Dictionary > Macronucleus

Macronucleus

Definition
noun, plural: macronuclei
The larger type of nucleus involved in non-reproductive functions (as opposed to the smaller micronucleus), and is a distinctive feature among ciliates since it only occurs in this group
Supplement
The ciliates are a group of protozoans that are known for their characteristic cilia, which are hair-like organelles as well as the presence of a macronucleus.1 A macronucleus is the larger nucleus in contrast to the smaller type of nucleus found in ciliates. The macronucleus is derived from the micronucleus by the process of DNA polytenisation.
The macronucleus is a polyploid in contrast to the micronucleus, which is diploid. The macronucleus contains multiple sets of chromosomes and in which the DNA is actively transcribed. It is involved in non-reproductive functions in cell metabolism and protein synthesis while the micronucleus is associated with reproduction.
The macronucleus undergoes direct division without mitosis (amitosis). It degenerates before conjugation, forming new macronucleus through karyogamy of the micronuclei.
Word origin: macro– (large) + nucleus
Synonym(s):

  • meganucleus

Compare:

  • micronucleus
  • See also:

    Reference(s):

    1 Cavalier-Smith, T. (2000). Flagellate megaevolution: the basis for eukaryote diversification. In: Leadbeater, B.S.C., Green, J.C. (eds.). The Flagellates. Unity, diversity and evolution. London: Taylor and Francis, pp. 361-390, p. 362.


    You will also like...

    squirrel
    Animal Water Regulation

    Animals adapt to their environment in aspects of anatomy, physiology, and behavior. This tutorial will help you understa..

    Plant Water Regulation
    Plant Water Regulation

    Plants need to regulate water in order to stay upright and structurally stable. Find out the different evolutionary adap..

    Water Cycle
    The Water Cycle

    The water cycle (also referred to as the hydrological cycle) is a system of continuous transfer of water from the air, s..

    Adaptation Tutorial
    Adaptation Tutorial

    Adaptation, in biology and ecology, refers to the process or trait through which organisms or the populations in a habit..

    Plant biology
    Plant Biology

    Plantlife can be studied at a variety of levels, from the molecular, genetic and biochemical level through organelles, c..

    Early Earth
    The Origins of Life

    This tutorial digs into the past to investigate the origins of life. The section is split into geological periods in the..

    Related Articles...

    No related articles found

    See all Related Topics