why is DNA unreactive/stable? (A level bio)

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SmartUnicorn
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I can't find solid answers online
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Kavita2002- QMUL
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I think its because DNA has hydrogen bonds. They are strong bonds so cannot break easily so maybe thats y they r unreactive. They are stable because they have a double helix structure. A binds to T with 2 H bonds and C binds with G with 3 H bonds.
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CJField
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(Original post by SmartUnicorn)
I can't find solid answers online
(Original post by kavita2002)
I think its because DNA has hydrogen bonds. They are strong bonds so cannot break easily so maybe thats y they r unreactive. They are stable because they have a double helix structure. A binds to T with 2 H bonds and C binds with G with 3 H bonds.
This is untrue as hydrogen bonds are very weak, in fact they aren't really bonds at all - but that is chemistry not biology. DNA is stable because it has a sugar-phosphate backbone which is linked by phosphodiester covalent bonds which are very strong. Combined with the helical structure, and the super-coiling of DNA, most of the DNA becomes hard to reach for chemicals.
Note the advantage of polynucleotides being joined by hydrogen bonds is that is can be easily split up by DNA helicase during semi conservative replication.
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SmartUnicorn
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(Original post by CJField)
This is untrue as hydrogen bonds are very weak, in fact they aren't really bonds at all - but that is chemistry not biology. DNA is stable because it has a sugar-phosphate backbone which is linked by phosphodiester covalent bonds which are very strong. Combined with the helical structure, and the super-coiling of DNA, most of the DNA becomes hard to reach for chemicals.
Note the advantage of polynucleotides being joined by hydrogen bonds is that is can be easily split up by DNA helicase during semi conservative replication.
thankyou!
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HarisMalik98
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Just to add on an extra point to CJField's answer;

RNA is composed of a ribose sugar, as opposed to deoxyribose in DNA. The ribose sugar has an extra -OH group on the second carbon in the ring (2'-OH) which makes RNA more susceptible to hydrolysis reactions (i.e. more "reactive").
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CJField
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(Original post by HarisMalik98)
Just to add on an extra point to CJField's answer;

RNA is composed of a ribose sugar, as opposed to deoxyribose in DNA. The ribose sugar has an extra -OH group on the second carbon in the ring (2'-OH) which makes RNA more susceptible to hydrolysis reactions (i.e. more "reactive").
oh that's interesting... would that be due to RNA needing to undergo processes like splicing?
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HarisMalik98
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(Original post by CJField)
oh that's interesting... would that be due to RNA needing to undergo processes like splicing?
I remember covering this a few years ago at uni, I think the main importance of the 2'-OH group in ribose sugars is more a structural point. The 2'-OH groups stabilise the hairpin structure and other secondary structural elements of RNA. The 2'-OH groups also facilitate protein binding to form RNA-protein complexes that aid in protein synthesis (e.g. ribonucleoproteins).

There might be other functions reported online in papers but I think that's the main ones.
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CJField
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(Original post by HarisMalik98)
I remember covering this a few years ago at uni, I think the main importance of the 2'-OH group in ribose sugars is more a structural point. The 2'-OH groups stabilise the hairpin structure and other secondary structural elements of RNA. The 2'-OH groups also facilitate protein binding to form RNA-protein complexes that aid in protein synthesis (e.g. ribonucleoproteins).

There might be other functions reported online in papers but I think that's the main ones.
oh right thank you
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