Search results
Results from the WOW.Com Content Network
Nucleosome free region typically spans for 200 nucleotides in S. cerevisiae [43] Well-positioned nucleosomes form boundaries of NFR. These nucleosomes are called +1-nucleosome and −1-nucleosome and are located at canonical distances downstream and upstream, respectively, from transcription start site.
Examples of different levels of nuclear architecture. Nuclear organization refers to the spatial organization and dynamics of chromatin within a cell nucleus during interphase. There are many different levels and scales of nuclear organization. At the smallest scale, DNA is packaged into units called nucleosomes, which
Because the human genome is so large, DNA must be condensed into chromatin, which consists of repeating units known as nucleosomes. Nucleosomes contain DNA and proteins called histones. The nucleosome core usually contains around 146 DNA base pairs wrapped around a histone octamer. [4]
As promoters are typically immediately adjacent to the gene in question, positions in the promoter are designated relative to the transcriptional start site, where transcription of DNA begins for a particular gene (i.e., positions upstream are negative numbers counting back from -1, for example -100 is a position 100 base pairs upstream).
Schematic representation of the assembly of the core histones into the nucleosome. In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei and in most Archaeal phyla. They act as spools around which DNA winds to create structural units called nucleosomes.
The major structures in DNA compaction: DNA, the nucleosome, the 10 nm "beads-on-a-string" fibre, the 30 nm fibre and the metaphase chromosome. In the nuclear chromosomes of eukaryotes, the uncondensed DNA exists in a semi-ordered structure, where it is wrapped around histones (structural proteins), forming a composite material called chromatin.
The handedness of the toroidal supercoils is opposite to those of plectonemes. Both plectonemes and toroidal supercoils can be either in a free form or restrained in a bound form with proteins. The best example of the bound toroidal supercoiling in biology is the eukaryotic nucleosome in which DNA wraps around histones. [20]
This opens up the usually tightly packed nucleosome and allows transcription machinery to come into contact with the DNA template, leading to gene transcription. [1]: 242 Repression of gene transcription is achieved by the reverse of this mechanism. The acetyl group is removed by one of the HDAC enzymes during deacetylation, allowing histones ...