Chromatin

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Published on December 10, 2021 9:51:43 AM ● Video Link: https://www.youtube.com/watch?v=WMOE-ONUDnw

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Chromatin, by Wikipedia https://en.wikipedia.org/wiki?curid=6933 / CC BY SA 3.0

#Molecular_genetics
#Nuclear_substructures
The major structures in DNA compaction: DNA, the nucleosome, the 10 nm beads on a stringchromatin fibre and the metaphase chromosome.
Chromatin is a complex of DNA and protein found in eukaryotic cells.
The primary function is to package long DNA molecules into more compact, denser structures.
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: DNA wraps around histone proteins, forming nucleosomes and the so-called beads on a string structure （euchromatin）.
Multiple histones wrap into a 30-nanometer fibre consisting of nucleosome arrays in their most compact form （heterochromatin）.
Higher-level DNA supercoiling of the 30-nm fibre produces the metaphase chromosome （during mitosis and meiosis）.
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.
Prokaryotic cells have entirely different structures for organizing their DNA （the prokaryotic chromosome equivalent is called a genophore and is localized within the nucleoid region）.
The overall structure of the chromatin network further depends on the stage of the cell cycle.
During interphase, the chromatin is stru...