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Bishal Paul posted an Question

April 16, 2021 • 18:34 pm

30 points

CSIR NET
Life Sciences

Explain the role of chromatin in gene expression

explain the role of chromatin in gene expression and please discuss it descriptively with illustration

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Krishan k jakhad

Chromatin remodeler enzymes can enzymatically change the distribution or composition of nucleosomes (histone octamers).
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Diagram sir
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ese bolo na beta ji.. diagrammatically you were asking for explanation only..
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Krishan k jakhad

Chromatin structure plays a key role in regulating gene expression by allowing DNA accessibility to transcriptional machinery and transcription factors..portions of the chromosomes remain highly condensed and heavily stained throughout the cell cycle. He named these regions “heterochromatin” to distinguish them from the regions showing variable staining and condensation, which he called “euchromatin.” The boundaries of heterochromatin as defined by such cytological analyses are not precise and may change in different tissues or with different analytical techniques. The primary packaging unit of chromatin is the nucleosome, composed of 147 bp of DNA wrapped around a histone octamer composed of two subunits each of the core histones H2A, H2B, H3, and H4. The histone globular domains are arranged in the interior of the nucleosome, while their unstructured tail domains project outwards where they are targets for a range of posttranslational modifications, including acetylation, phosphoryla- tion, methylation, ADP-ribosylation, ubiquitination, sumoylation, and biotiny- lation. These modifications have been proposed to regulate genomic function by influencing chromatin structure both by altering the biophysical contacts between DNA and histones and by providing specific binding sites for different classes of chromatin-binding proteins. In general, the “activating” modifications consist of methylated H3K4, H3K36, and H3K79, while the “silencing” modifications are composed of methylated H3K9, H3K27, and H4K20.
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please give the illustration
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In eukaryotes, the tight or loose packaging of the genes in chromatin (DNA plus specific proteins) can control whether the genes can be expressed to form their encoded product. Chromatin is usually not "permissive" but it can be modified in specific areas to open it up for transcription of the genes.
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