Dictionary > Constitutive heterochromatin

Constitutive heterochromatin

Definition
noun
Regions on chromosomes that are condensed permanently, genetically inactive, and always in the same position on homologous chromosomes
Supplement
Heterochromatin pertains to the darkly stained regions of the chromatin in the interphase nucleus. The lightly stained regions are referred to as euchromatin. The heterochromatic regions indicate tightly packed genetic material and undergo relatively little change in the degree of condensation as it passes through the cell cycle. They are usually found in the periphery of the nucleus. It is described to be genetically inactive due to the inaccessibility to polymerases, thus, evading transcription. There are different heterochromatin varieties, e.g. constitutive heterochromatin and facultative heterochromatin.
Constitutive heterochromatin is mainly found at centromeric and telomeric regions. In humans, heterochromatic regions abound in chromosomes 1, 9, 16, 19, and on Y chromosome.1 The less condensed heterochromatin is the facultative heterochromatin. C banding may be employed to visualize and identify constitutive heterochromatic regions. Facultative heterochromatin does not stain with C banding technique.
Structurally, constitutive heterochromatin is repetitive whereas facultative heterochromatin is not. Furthermore, constitutive heterochromatin is transcriptionally inactive at all times. In contrast, facultative heterochromatin may at time lose its condensed state and become transcriptionally active.
Compare:

See also:

  • heterochromatin
  • chromatin
  • nucleus
  • cell cycle
  • Reference(s):

    1 Strachan, T. & Read, A. (2004). Human Molecular Genetics 3. Garland Publishing. pp. 256–295.


    You will also like...

    IQ, Creativity and Learning
    IQ, Creativity and Learning

    Human intelligence provided the means to utilize abstract ideas and implement reasoning. This tutorial takes a further l..

    Biological Energy
    ATP & ADP – Biological Energy

    ATP is the energy source that is typically used by an organism in its daily activities. The name is based on its structu..

    Cells in different stages of meiosis
    Meiosis – The Genetics of Reproduction

    Meiosis is a form of cell division that creates gametes. It is comprised of two divisions that in the end, the resulting..

    Developmental Biology
    Developmental Biology

    Developmental biology is a biological science that is primarily concerned with how a living thing grows and attains matu..

    An artist's depiction of the origin of amphibians
    Amphibians & Early Reptiles

    Obtaining air outside an aquatic environment required species to acquire suitable adaptations, and this was the case of ..

    running freshwater community
    Running Water Freshwater Community Factors

    This tutorial noted some of the physical and chemical factors that provide the framework of a running water community in..

    Related Articles...

    No related articles found

    See all Related Topics