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...

    A sperm cell fertilizing an ovum
    Human Reproduction and Fertilization

    For human species to obviate extinction, reproductive mature adults should be producing viable offspring in order to con..

    takahē
    Takahē (Porphyrio hochstetteri)

    Meet the colorful takahē, an extremely rare flightless bird. Find out more about its unique features and why they matte..

    Biosecurity and Biocontrol
    Biosecurity and Biocontrol

    This lesson explores the impact of biosecurity threats, and why they need to be identified and managed. Examples to incl..

    Biological Cell Defense
    Biological Cell Defense

    Organisms employ different strategies to boost its defenses against antigens. Humans have an immune system to combat pat..

    Pikas are an indicator species for climate change
    Indicator Species and Endangered Species

    Certain species are capable of expressing characteristics indicative of the state of the ecosystem they occupy. They are..

    mRNA
    Protein Synthesis

    Part of the genetic information is devoted to the synthesis of proteins. mRNA, a type of RNA, is produced as a transcri..

    Related Articles...

    No related articles found

    See all Related Topics