Forms of DNA: Difference between revisions
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== A comparative representation of the three forms of DNA == | |||
''Sources'' <ref>Nucleic Acid Canonical Coordinates http://nucleix.mbu.iisc.ac.in/nacc/index.html</ref> | ''Sources'' <ref>Nucleic Acid Canonical Coordinates http://nucleix.mbu.iisc.ac.in/nacc/index.html</ref> | ||
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</jmol> | </jmol> | ||
== Helical Parameters of the three forms of DNA == | |||
DNA is a very flexible molecule and has the ability to exist in various forms based on the environmental conditions. Naturally occurring DNA double helices are classified into A, B and Z-types. A and B-forms of DNA are the right handed forms whereas [[Z-DNA]] is the left handed form. When hydrated the DNA generally assumes B-form. The A conformation is found when there is little water to interact with the helix and is also the conformation adopted by the RNA. The formation of Z-DNA occurs with the methylation of deoxycytosine residues and also during transcription where negative supercoiling stabilizes it. | DNA is a very flexible molecule and has the ability to exist in various forms based on the environmental conditions. Naturally occurring DNA double helices are classified into A, B and Z-types. A and B-forms of DNA are the right handed forms whereas [[Z-DNA]] is the left handed form. When hydrated the DNA generally assumes B-form. The A conformation is found when there is little water to interact with the helix and is also the conformation adopted by the RNA. The formation of Z-DNA occurs with the methylation of deoxycytosine residues and also during transcription where negative supercoiling stabilizes it. | ||
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|Diameter of helix [Å]||align="right"| 23||align="right"| 20||align="right"| 18 | |Diameter of helix [Å]||align="right"| 23||align="right"| 20||align="right"| 18 | ||
|- | |- | ||
|Glycosidic bond configuration<br | |Glycosidic bond configuration<br>dA,dT,dC<br>dG ||align="center"| <br>anti<br>anti ||align="center"| <br>anti<br>anti ||align="center"| <br>anti<br>syn | ||
|- | |- | ||
|[[Sugar ring pucker|Sugar pucker]]<br | |[[Sugar ring pucker|Sugar pucker]]<br>dA,dT,dC<br>dG ||align="center"| <br>C3'-endo<br>C3'-endo ||align="center"|<br> C2'-endo<br>C2'-endo ||align="center"| <br>C2'-endo<br>C3'-endo | ||
|- | |- | ||
|Intrastrand phosphate-phosphate distance [Å] <br | |Intrastrand phosphate-phosphate distance [Å] <br>dA,dT,dC<br>dG ||align="center"| <br>5.9<br>5.9||align="center"| <br>7.0<br>7.0||align="center"| <br>7.0<br> 5.9 | ||
|- | |- | ||
|colspan="4"|''Sources: <ref name="Rich1984">PMID:6383204</ref><ref name="Rich1979">PMID: 514347</ref><ref> Sinden, Richard R (1994-01-15). ''DNA structure and function'' (1st ed.). Academic Press. pp. 398. ISBN 0-12-645750-6.</ref> | |colspan="4"|''Sources: <ref name="Rich1984">PMID:6383204</ref><ref name="Rich1979">PMID: 514347</ref><ref> Sinden, Richard R (1994-01-15). ''DNA structure and function'' (1st ed.). Academic Press. pp. 398. ISBN 0-12-645750-6.</ref> | ||
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</StructureSection> | </StructureSection> | ||
== References== | == See also == | ||
* [[DNA - History of the discovery and current applications (Hebrew)]] | |||
* [[DNA]] | |||
* [[Z-DNA]] | |||
== References == | |||
<references/> | <references/> | ||
