Navigation Links
Centromere


The centromere is a region of a eukaryotic chromosome where the kinetochore is assembled. Thus, it is the site where spindle fibers of the mitotic spindle attach to the chromosome during mitosis. It is also the site of the primary constriction visible in microscopy images of chromosomes.

In most eukaryotes, the centromere has no defined DNA sequence. It typically consists of large arrays of repetitive DNA where the sequence within individual repeat elements is similar but not identical. In humans, the centromeric repeat unit is called α-satellite. However, repeats of α-satellite are not sufficient to cause the assembly of a kinetochore, and there are functioning centromeres with no α-satellite DNA.

Epigenetic inheritance plays a major role in specifying the centromere in most organisms. The daughter chromosomes will assemble centromeres in the same place as the parent chromosome, independent of sequence. However, there must still be some original way in which the centromere is specified, even if it is subsequently propagated epigenetically. In rare cases in humans, neocentromeres can form at new sites on the chromosome. This must be coupled with the inactivation of the previous centromere since chromosomes with two functional centromeres (dicentric chromosomes) will result in chromosome breakage during mitosis.

The centromeric DNA is normally in a heterochromatin state, which is probably essential for its function. In this chromatin, the normal histone H3 is replaced with CENP-A, a centromere-specific variant. The presence of CENP-A is believed to be important for the assembly of the kinetochore on the centromere and may play a role in the epigenetic inheritance of the centromere site.

In the yeast Schizosaccharomyces pombe (and likely in other eukaryotes) the formation of centromeric heterochromatin is connected to RNAi*. In nematodes such as Caenorhabditis elegans and in some plants, chromosomes are "holocentric" indicating that there is not a primary site of microtubule attachments or a primary constriction, and a "diffuse" kinetochore assembles along the entire length of the chromosome.

See also: Genetics -- Cell biology

External links


'"/>


(Date:7/25/2014)... Prediabetes and Diabetes increasingly consume the healthcare ... immediate attention. , To address the ... impacting low-and middle-income countries, global leaders in ... research in diabetes prevention and development of ... important text. , This book on ...
(Date:7/25/2014)... tractography (DTT), which is derived from diffusion tensor ... motor tracts, such as the corticospinal tract, the ... The corticospinal tract is known to be a ... human brain. Several studies have reported on injury ... addition, some studies have demonstrated recovery of a ...
(Date:7/25/2014)... detected an unknown interaction between microorganisms and salt. When ... droplet of salt water and is left to dry, ... biosaline 3D morphologically complex formations, where they hibernate. Afterwards, ... discovery was made by chance with a home microscope, ... journal and may help to find signs of ...
Breaking Biology News(10 mins):What constitutes an effective response to the global 'diabesity' tsunami? 2Bacteria manipulate salt to build shelters to hibernate 2
... field trials of Miscanthus x giganteus , a towering ... yields, though reduced somewhat after five years of growth, are ... ), another perennial grass used as a bioenergy feedstock. ... yields found in earlier studies of the crop in Europe, ...
... Sciences (AIBS) has selected three individuals as winners of ... This is the third year AIBS has sponsored ... members of the scientific community to showcase for the ... informing natural resources management, addressing climate change, improving human ...
... For some 5,000 years, cultivated silkworms have been spinning ... finest clothing. But current dyeing practices produce wastewater that ... a new, "greener" dyeing method in which they coax ... leaves. Their findings are published in the journal ...
Cached Biology News:The first decade: Team reports on US trials of bioenergy grasses 2The first decade: Team reports on US trials of bioenergy grasses 3AIBS announces winners of Faces of Biology photo competition 2
Other biology definitionOther Tags