Chromatin
A complex of DNA, histones and nonhistone chromosomal proteins, which condense to make up the chromosomes found in eukaryotic nuclei [1]. 145 bp of DNA is wound into a left-handed superhelix [2] around 8 histones with up to 50 bp[3] linking to the next "bead on a string". Each of these repeating units is a nucleosome.
Formation of Chromatin Fibres
Before the formation of chromatin fibres, nuclesomes are lined up with clusters of histones packed together and connected by linker DNA. The 10nm(in diameter) chain of nucleosomes is further condensed to form a thicker structure which is 30nm in diameter. The formation of the chromatin fibre is due to the change in salt concentration of the nuclear solution present in the cell. The packaging of the fibre is seen to be in a zigzag structure by the interlocking of fibres present within it.[4]
Folding and Formation of a Chromosome
Heterochromatin and euchromatins are being labelled to distinguish the way in how the chromatins are folded. Heterochromatins are tighly packed while euchromatins are not as compact as euchromatins. Both of these contain DNA, heterochromatin having its DNA in an inactive state while euchromatin has its DNA in an active state. The condensation and compacting of euchromatin in cell division, makes the chromatin to be fully active and with that, give rise to the clear formation, picture and structure ofchromosome.[5]
Chromatin is formed to strengthen the DNA and decrease it's volume in the cell, thus preventing damage.
References
- ↑ Alberts, B. et al., 2007. Molecular Biology of the Cell. 5th ed. s.l.:Garland Science. p.G:7
- ↑ Berg, Jeremy M., et al. 2011. Biochemistry. 7th Edition. Palgrave MacMillan. p.976
- ↑ Hardin, J., Bertoni, G. & Kleinsmith, L.J (2012). Becker's World of the Cell . 8th ed. California: Pearson. 533.
- ↑ Hardin, J., Bertoni, G. & Kleinsmith, L.J (2006). Becker's World of the Cell . 8th ed. California: Pearson. 533.
- ↑ Hardin, J., Bertoni, G. & Kleinsmith, L.J (2006). Becker's World of the Cell . 8th ed. California: Pearson. 533.