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...

    Bryophytes
    Bryophytes

    Bryophytes (nonvascular plants) are a plant group characterized by lacking vascular tissues. They include the mosses, th..

    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..

    Golgi apparatus (3-D illustration)
    Role of Golgi Apparatus & Endoplasmic Reticulum in Protein Synthesis

    The endoplasmic reticulum and Golgi apparatus are the organelles involved in the translation step of protein synthesis a..

    Ecological Research Measuring & Analysis
    Ecological Research: Measuring & Analysis

    This lesson is about the methods used for ecological research, such as quadrat and transect sampling, canopy fogging, an..

    Crossing Over and Genetic Diversity
    Inheritance and Probability

    Gregor Mendel, an Austrian monk, is most famous in this field for his study of the phenotype of pea plants, including ..

    Adaptive Radiation
    Adaptive Radiation

    The diversification of several new species from a recent ancestral source, each adapted to utilize or occupy a vacant ad..

    Related Articles...

    No related articles found

    See all Related Topics