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Usually, DNA condensation is defined as "the collapse of extended DNA chains into compact, orderly particles containing only one or a few molecules". [3] This definition applies to many situations in vitro and is also close to the definition of DNA condensation in bacteria as "adoption of relatively concentrated, compact state occupying a ...
Each chromosome consists of two closely associated sister chromatids along their entire length. The chromosomes appear as distinct, well-defined threadlike structures under the microscope. [ 3 ] [ 4 ] Sex chromosomes , however, are not wholly identical, and only exchange information over a small region of homology called the pseudoautosomal ...
The nucleosome is the basic unit of DNA condensation and consists of a DNA double helix bound to an octamer of core histones (2 dimers of H2A and H2B, and an H3/H4 tetramer). About 147 base pairs of DNA coil around 1 octamer, and ~20 base pairs are sequestered by the addition of the linker histone (H1), and various length of "linker" DNA (~0 ...
This relaxation can be reversed by deacetylation catalyzed by HDAC activity. Relaxed, transcriptionally active DNA is referred to as euchromatin. More condensed (tightly packed) DNA is referred to as heterochromatin. Condensation can be brought about by processes including deacetylation and methylation. [1]
[55] [56] Condensin II is present within the cell nucleus during interphase and participates in an early stage of chromosome condensation within the prophase nucleus. On the other hand, condensin I is present in the cytoplasm during interphase, and gains access to chromosomes only after the nuclear envelope breaks down (NEBD) at the end of ...
It is visible on a chromosome during the prophase of meiosis and mitosis. Giant banded chromosomes resulting from the replication of the chromosomes and the synapsis of homologs without cell division is a process called endomitosis. These chromosomes consist of more than 1000 copies of the same chromatid that are aligned and produce alternating ...
[4] [5] [6] SMC1 and SMC3 also have functions in the repair of DNA double-strained breaks in the process of homologous recombination. [7] Likewise, a pair of SMC2 and SMC4 acts as the core of the condensin complexes implicated in chromosome condensation. [8] [9] SMC2 and SMC4 have the function of DNA repair as well. Condensin I plays a role in ...
Such modifications affect the binding affinity between histones and DNA, and thus loosening or tightening the condensed DNA wrapped around histones, e.g., Methylation of specific lysine residues in H3 and H4 causes further condensation of DNA around histones, and thereby prevents binding of transcription factors to the DNA that lead to gene ...