In eukaryotes, the DNA is packaged in the form of a nucleoprotein complex called chromatin, which carries the vital hereditary information. Chromatin is localized in the nucleus and organized into the chromosomes. Heterochromatin is the tightly coiled chromosomal material that stains deeply during interphase of the cell cycle and is believed to be genetically inactive.
Emil Heitz described heterochromatin based on histological observations, when he found chromosomal regions extremely condensed and dark in color in the interphase nucleus. The rest of the nucleus is occupied by euchromatin or the true chromatin, which is diffusely organized and relatively light in color. He also hypothesized that “euchromatin is genetically active, heterochromatin genetically passive.” Although this is not entirely true, it paved the way for major discoveries in chromatin research. Over the time, with the development of improved staining methods and the electron microscopy, it...
KeywordsProliferate Cell Nuclear Antigen Histone Variant Replication Factor Origin Recognition Complex Chromatin Assembly
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