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Chromatin is a complex of DNA and protein found in eukaryotic cells. [1] 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 ...
In contrast to most eukaryotic cells, mature sperm cells largely use protamines to package their genomic DNA, most likely to achieve an even higher packaging ratio. [17] Histone equivalents and a simplified chromatin structure have also been found in Archaea, [18] suggesting that eukaryotes are not the only organisms that use nucleosomes.
However, in order for the cell to function, proteins must be able to access the sequence information contained within the DNA, in spite of its tightly-packed nature. Hence, the cell has a number of mechanisms in place to control how DNA is organized. [4] Moreover, nuclear organization can play a role in establishing cell identity.
Histone H2A is one of the five main histone proteins involved in the structure of chromatin in eukaryotic cells. The other histone proteins are: H1, H2B, H3 and H4. The crystal structure of the nucleosome core particle consisting of H2A, H2B, H3 and H4 core histones, and DNA. The view is from the top through the superhelical axis.
Eukaryotic chromosomes are also stored in the cell nucleus, while chromosomes of prokaryotic cells are not stored in a nucleus. Eukaryotic chromosomes require a higher level of packaging to condense the DNA molecules into the cell nucleus because of the larger amount of DNA. This level of packaging includes the wrapping of DNA around proteins ...
Core histones are found in the nuclei of eukaryotic cells and in most Archaeal phyla, but not in bacteria. [18] The unicellular algae known as dinoflagellates were previously thought to be the only eukaryotes that completely lack histones, [23] but later studies showed that their DNA still encodes histone genes. [24]
Basic units of chromatin structure. Histone H2B is a structural protein that helps organize eukaryotic DNA. [5] It plays an important role in the biology of the nucleus where it is involved in the packaging and maintaining of chromosomes, [5] regulation of transcription, and replication and repair of DNA. [2]
DNA is one of the stiffest natural polymers, yet it is also one of the longest molecules. The persistence length of double-stranded DNA (dsDNA) is a measure of its stiffness or flexibility, which depends on the DNA sequence and the surrounding environment, including factors like salt concentration, pH, and temperature.