File Name: chromatin structure and function .zip
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Chromatin is a complex of DNA and protein found in eukaryotic cells. This prevents the strands from becoming tangled and also plays important roles in reinforcing the DNA during cell division , preventing DNA damage , and regulating gene expression and DNA replication. During mitosis and meiosis , chromatin facilitates proper segregation of the chromosomes in anaphase ; the characteristic shapes of chromosomes visible during this stage are the result of DNA being coiled into highly condensed chromatin. The primary protein components of chromatin are histones , which bind to DNA and function as "anchors" around which the strands are wound. In general, there are three levels of chromatin organization:. Many organisms, however, do not follow this organization scheme. For example, spermatozoa and avian red blood cells have more tightly packed chromatin than most eukaryotic cells, and trypanosomatid protozoa do not condense their chromatin into visible chromosomes at all.
Chromatin is a mass of genetic material composed of DNA and proteins that condense to form chromosomes during eukaryotic cell division. Chromatin is located in the nucleus of our cells. The primary function of chromatin is to compress the DNA into a compact unit that will be less voluminous and can fit within the nucleus. Chromatin consists of complexes of small proteins known as histones and DNA. Histones help organize DNA into structures called nucleosomes by providing a base on which the DNA can be wrapped around. A nucleosome consists of a DNA sequence of about base pairs that is wrapped around a set of eight histones called an octamer. The nucleosome is further folded to produce a chromatin fiber.
Chromatin is a complex of macromolecules composed of DNA, RNA, and protein, which is found inside the nucleus of eukaryotic cells. Chromatin exists in two forms: heterochromatin condensed and euchromatin extended. The nucleosome can be further folded to produce the chromatin fiber. Chromatin fibers are coiled and condensed to form chromosomes. Chromatin makes it possible for a number of cell processes to occur including DNA replication, transcription, DNA repair, genetic recombination, and cell division. People often confuse these three terms: chromatin , chromosome, and chromatid. While all of those three structures are composed of DNA and proteins within the nucleus, each is uniquely defined.
The packaging of chromatin into the nucleus of a eukaryotic cell requires an extraordinary degree of compaction and physical organization. In recent years, it has been shown that this organization is dynamically orchestrated to regulate responses to exogenous stimuli as well as to guide complex cell-type-specific developmental programs. Gene expression is regulated by the compartmentalization of functional domains within the nucleus, by distinct nucleosome compositions accomplished via differential modifications on the histone tails and through the replacement of core histones by histone variants. In this review, we focus on these aspects of chromatin organization and discuss novel approaches such as live cell imaging and photobleaching as important tools likely to give significant insights into our understanding of the very dynamic nature of chromatin and chromatin regulatory processes. We highlight the contribution plant studies have made in this area showing the potential advantages of plants as models in understanding this fundamental aspect of biology. In eukaryotic cells the nuclear DNA does not appear naked but is associated with many proteins to form the complex called chromatin.
Antigenic variation ; Epigenetic regulation ; Genome organization ; Histone modifications ; Histone variants ; Histones ; Nuclear architecture. In eukaryotes, the genetic material is packaged into a higher-order structure called chromatin. Chromatin is composed of DNA, histone, and nonhistone proteins as well as noncoding RNAs and organizes the genetic material into district chromosomes. While in plasmodia the 14 chromosomes do not appear to condense into discrete structures during cell division, chromatin is nonetheless essential for the replication and segregation of the chromosomes to the daughter cells. Our understanding of chromatin-mediated epigenetics in plasmodia principally results from studies in P.
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