Chromatin: Difference between revisions
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A complex of [[DNA|DNA]], [[Histones|histones]] and [[Non-histone chromosomal proteins|nonhistone chromosomal proteins]], which condense to make up the [[Chromosomes|chromosomes]] found in [[Eukaryote|eukaryotic]] [[Nucleus|nuclei]] <ref>Alberts, B. et al., 2007. Molecular Biology of the Cell. 5th ed. s.l.:Garland Science. p.G:7</ref>. 145 [[Base pair|bp]] of DNA is wound into a left-handed superhelix <ref>Berg, Jeremy M., et al. 2011. Biochemistry. 7th Edition. Palgrave MacMillan. p.976</ref> around 8 [[Histones|histones]] with up to 50 bp<ref>Hardin, J., Bertoni, G. &amp;amp; Kleinsmith, L.J (2012). Becker's World of the Cell . 8th ed. California: Pearson. 533.</ref> linking to the next "bead on a string". Each of these repeating units is a [[Nucleosome|nucleosome]].<br> | A complex of [[DNA|DNA]], [[Histones|histones]] and [[Non-histone chromosomal proteins|nonhistone chromosomal proteins]], which condense to make up the [[Chromosomes|chromosomes]] found in [[Eukaryote|eukaryotic]] [[Nucleus|nuclei]] <ref>Alberts, B. et al., 2007. Molecular Biology of the Cell. 5th ed. s.l.:Garland Science. p.G:7</ref>. 145 [[Base pair|bp]] of DNA is wound into a left-handed superhelix <ref>Berg, Jeremy M., et al. 2011. Biochemistry. 7th Edition. Palgrave MacMillan. p.976</ref> around 8 [[Histones|histones]] with up to 50 bp<ref>Hardin, J., Bertoni, G. &amp;amp;amp; Kleinsmith, L.J (2012). Becker's World of the Cell . 8th ed. California: Pearson. 533.</ref> linking to the next "bead on a string". Each of these repeating units is a [[Nucleosome|nucleosome]].<br> | ||
=== Formation of Chromatin Fibres === | === Formation of Chromatin Fibres === | ||
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Before the formation of chromatin fibres, [[Nucleosome|nuclesomes]] are lined up with clusters of [[Histones|histones]] packed together and connected by linker DNA. Each nucleosome is made up of an octamer of histone protein subunits. These subunits are H2A, H2B,H3 and H4. A tetramer of H3 and H4 has two dimers of H2A and H2B attached. Then 147 base pairs of DNA is wrapped twice around the subunits to create a stable single nucleosome. | Before the formation of chromatin fibres, [[Nucleosome|nuclesomes]] are lined up with clusters of [[Histones|histones]] packed together and connected by linker DNA. Each nucleosome is made up of an octamer of histone protein subunits. These subunits are H2A, H2B,H3 and H4. A tetramer of H3 and H4 has two dimers of H2A and H2B attached. Then 147 base pairs of DNA is wrapped twice around the subunits to create a stable single nucleosome. | ||
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 | 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<ref>Hardin, J., Bertoni, G. &amp;amp;amp;amp;amp; Kleinsmith, L.J (2006). Becker's World of the Cell . 8th ed. California: Pearson. 533.</ref>. | ||
=== Folding and Formation of a Chromosome === | === Folding and Formation of a Chromosome === | ||
[[Heterochromatin|Heterochromatin]] and [[Euchromatin|euchromatins]] are being labelled to distinguish the way in how the chromatins are folded. Heterochromatins are tighly packed while euchromatins are not as compact. 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 of[[Chromosomes|chromosome]] | [[Heterochromatin|Heterochromatin]] and [[Euchromatin|euchromatins]] are being labelled to distinguish the way in how the chromatins are folded. Heterochromatins are tighly packed while euchromatins are not as compact. 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 of [[Chromosomes|chromosome]]<ref>Hardin, J., Bertoni, G. &amp;amp;amp;amp; Kleinsmith, L.J (2006). Becker's World of the Cell . 8th ed. California: Pearson. 533.</ref>. | ||
Chromatin is formed to strengthen the DNA and decrease it's volume in the [[Cell|cell]], thus preventing damage. | Chromatin is formed to strengthen the DNA and decrease it's volume in the [[Cell|cell]], thus preventing damage. | ||
=== References === | === References === | ||
<references /><br> | <references /><br> | ||
Revision as of 15:52, 18 November 2016
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. Each nucleosome is made up of an octamer of histone protein subunits. These subunits are H2A, H2B,H3 and H4. A tetramer of H3 and H4 has two dimers of H2A and H2B attached. Then 147 base pairs of DNA is wrapped twice around the subunits to create a stable single nucleosome.
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. 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 of chromosome[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. &amp;amp; Kleinsmith, L.J (2012). Becker's World of the Cell . 8th ed. California: Pearson. 533.
- ↑ Hardin, J., Bertoni, G. &amp;amp;amp;amp; Kleinsmith, L.J (2006). Becker's World of the Cell . 8th ed. California: Pearson. 533.
- ↑ Hardin, J., Bertoni, G. &amp;amp;amp; Kleinsmith, L.J (2006). Becker's World of the Cell . 8th ed. California: Pearson. 533.