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The precise structure of the chromatin fiber in the cell is not known in detail. [10] This level of chromatin structure is thought to be the form of heterochromatin, which contains mostly transcriptionally silent genes. Electron microscopy studies have demonstrated that the 30 nm fiber is highly dynamic such that it unfolds into a 10 nm fiber ...
Commonly, many people think the structure of a chromosome is in an "X" shape. But this is only present when the cell divides. Researchers have now been able to model the structure of chromosomes when they are active. This is extremely important because the way that DNA folds up in chromosome structures is linked to the way DNA is used.
The concentration and specific composition of histones used can determine local chromatin structure. For example, euchromatin is a form of chromatin with low nucleosome concentration - here, the DNA is exposed, promoting interactions with gene expression, replication, and organizational machinery.
The solenoid structure can increase this to be 40 times smaller. [2] When DNA is compacted into the solenoid structure can still be transcriptionally active in certain areas. [7] It is the secondary chromatin structure that is important for this transcriptional repression as in vivo active genes are assembled in large tertiary chromatin ...
Suggested by the idea that the structure of chromatin can be modified to allow or deny access of transcription activators, regulatory functions of histone acetylation and deacetylation can have implications with genes that cause other diseases. Studies on histone modifications may reveal many novel therapeutic targets.
Bottom: Two tomato SCs with the chromatin removed, allowing kinetochores ("ball-like" structures) at centromeres to be revealed. The synaptonemal complex ( SC ) is a protein structure that forms between homologous chromosomes (two pairs of sister chromatids ) during meiosis and is thought to mediate synapsis and recombination during prophase I ...
Membrane attack complex (Terminal complement complex C5b-9) A membrane attack complex attached to a pathogenic cell The membrane attack complex (MAC) or terminal complement complex (TCC) is a complex of proteins typically formed on the surface of pathogen cell membranes as a result of the activation of the host's complement system, and as such is an effector of the immune system.