DNA: Difference between revisions
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== Features of a DNA Molecule == | == Features of a DNA Molecule == | ||
< | <StructureSection load='B-DNA.pdb' size='540' frame='true' align='left' caption='B-DNA' scene ='User:Adithya_Sagar/Sandbox_DNA/B-dna/4'> | ||
=== Double Helix === | === Double Helix === | ||
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A DNA double strand can be separated into two single strands by breaking the hydrogen bonds between them. This is known as DNA denaturation. Thermal energy provided by heating can be used to melt or denature DNA. Molecules with rich GC content are more stable and thus denature at higher temperatures compared to the ones with higher AT content. The melting temperature is defined as the temperature at which half the DNA strands are in double helical state and half are in random coil state.<ref>PMID: 9465037</ref> The denatured DNA single strands have an ability to renature and form double stranded DNA again. | A DNA double strand can be separated into two single strands by breaking the hydrogen bonds between them. This is known as DNA denaturation. Thermal energy provided by heating can be used to melt or denature DNA. Molecules with rich GC content are more stable and thus denature at higher temperatures compared to the ones with higher AT content. The melting temperature is defined as the temperature at which half the DNA strands are in double helical state and half are in random coil state.<ref>PMID: 9465037</ref> The denatured DNA single strands have an ability to renature and form double stranded DNA again. | ||
=== Grooves === | === Grooves === | ||
< | In a <scene name='DNA/Bdnasf/1'>DNA double helix</scene> the <scene name='User:Adithya_Sagar/Workbench_newDNA/B-dna/16'>beta-glycosyl bonds</scene> between C<sub>1'</sub>-N<sub>1</sub> branch off from one side of the base pair and do not lie opposite to each other. This results in unequally spaced sugar-phosphate backbones and gives rise to two grooves: the | ||
<scene name='DNA/Major_groove/2'>major groove</scene> and the <scene name='DNA/Major_groove/4'>minor groove</scene> of different width and depth. The minor groove is at the O<sub>2</sub> side of base pair and the major groove is on the opposite side.The floor of major groove is filled with nitrogen and oxygen atoms that project inward whereas in the minor groove they project outward. The larger size of major groove allows for the binding of DNA specific proteins.<ref name="Saenger"> Saenger, Wolfram (1984). ''Principles of Nucleic Acid Structure '' (1st ed). Springer-Verlag. pp. 398. ISBN 0-12-645750-6.</ref><ref name='Watson'> Watson, James D, Nancy H. Hopkins, Jeffrey W. Roberts, Joan Argetsinger Steitz, Alan M.Weiner ''Molecular Biology of Gene'' (4th ed.). The Benjamin/Cummings Publishing Company Inc.pp. 239-249. ISBN 0-8053-9612-8</ref> | <scene name='DNA/Major_groove/2'>major groove</scene> and the <scene name='DNA/Major_groove/4'>minor groove</scene> of different width and depth. The minor groove is at the O<sub>2</sub> side of base pair and the major groove is on the opposite side.The floor of major groove is filled with nitrogen and oxygen atoms that project inward whereas in the minor groove they project outward. The larger size of major groove allows for the binding of DNA specific proteins.<ref name="Saenger"> Saenger, Wolfram (1984). ''Principles of Nucleic Acid Structure '' (1st ed). Springer-Verlag. pp. 398. ISBN 0-12-645750-6.</ref><ref name='Watson'> Watson, James D, Nancy H. Hopkins, Jeffrey W. Roberts, Joan Argetsinger Steitz, Alan M.Weiner ''Molecular Biology of Gene'' (4th ed.). The Benjamin/Cummings Publishing Company Inc.pp. 239-249. ISBN 0-8053-9612-8</ref> | ||
===Tautomeric forms of bases=== | ===Tautomeric forms of bases=== | ||
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The hydrogen atoms on the bases move from nitrogen or oxygen atom on ring to another through shifts known as tautomeric shifts. However the hydrogens have preferred atomic locations. Based on the movement of hydrogen atoms the nitrogen atoms are in amino or imino configuration and the oxygen atoms are either in keto or enol forms. There is a preference for the amino and keto forms respectively which is very crucial for the biological functioning of DNA as it leads to the specificity in base pairing and thus complementarity of the chains.<ref name='Watson'> Watson, James D, Nancy H. Hopkins, Jeffrey W. Roberts, Joan Argetsinger Steitz, Alan M.Weiner ''Molecular Biology of Gene'' (4th ed.). The Benjamin/Cummings Publishing Company Inc.pp. 239-249. ISBN 0-8053-9612-8</ref> | The hydrogen atoms on the bases move from nitrogen or oxygen atom on ring to another through shifts known as tautomeric shifts. However the hydrogens have preferred atomic locations. Based on the movement of hydrogen atoms the nitrogen atoms are in amino or imino configuration and the oxygen atoms are either in keto or enol forms. There is a preference for the amino and keto forms respectively which is very crucial for the biological functioning of DNA as it leads to the specificity in base pairing and thus complementarity of the chains.<ref name='Watson'> Watson, James D, Nancy H. Hopkins, Jeffrey W. Roberts, Joan Argetsinger Steitz, Alan M.Weiner ''Molecular Biology of Gene'' (4th ed.). The Benjamin/Cummings Publishing Company Inc.pp. 239-249. ISBN 0-8053-9612-8</ref> | ||
</StructureSection> | |||
==Forms of DNA== | ==Forms of DNA== | ||
