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Thus, acetylation of histones is known to increase the expression of genes through transcription activation. Deacetylation performed by HDAC molecules has the opposite effect. By deacetylating the histone tails, the DNA becomes more tightly wrapped around the histone cores, making it harder for transcription factors to bind to the DNA.
Condensation of long double-helical DNAs is a sharp phase transition, which takes place within a narrow interval of condensing agent concentrations.[ref] Since the double helices come very closely to each other in the condensed phase, this leads to the restructuring of water molecules, which gives rise to the so-called hydration forces.[ref] To ...
Heterochromatin is a tightly packed form of DNA or condensed DNA, which comes in multiple varieties. These varieties lie on a continuum between the two extremes of constitutive heterochromatin and facultative heterochromatin. Both play a role in the expression of genes.
Around 146 base pairs (bp) of DNA wrap around this core particle 1.65 times in a left-handed super-helical turn to give a particle of around 100 Angstroms across. [8] The linker histone H1 binds the nucleosome at the entry and exit sites of the DNA, thus locking the DNA into place [9] and allowing the formation of higher order structure. The ...
The buoyant density of most DNA is 1.7g/cm 3. [11] DNA does not usually exist as a single strand, but instead as a pair of strands that are held tightly together. [9] [12] These two long strands coil around each other, in the shape of a double helix.
In nature, DNA can form three structures, A-, B-, and Z-DNA. A- and B-DNA are very similar, forming right-handed helices, whereas Z-DNA is a left-handed helix with a zig-zag phosphate backbone. Z-DNA is thought to play a specific role in chromatin structure and transcription because of the properties of the junction between B- and Z-DNA.
When it comes to insects' DNA, humans have a bit less in common. For example, fruit flies share 61 percent of disease-causing genes with humans, which was important when NASA studied the bugs to ...
DNA supercoiling is important for DNA packaging within all cells. Because the length of DNA can be thousands of times that of a cell, packaging this genetic material into the cell or nucleus (in eukaryotes) is a difficult feat. Supercoiling of DNA reduces the space and allows for DNA to be packaged.