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Hi! I had a question about AT and GC pairs in DNA. Since AT base pairs have only 2 hydrogen-bonding sites and GC has 3 hydrogen bonding sites, is GC stronger? Or are the bond strengths of AT and GC pretty comparable because they both are able to hydrogen bond? I was wondering if that 3rd h-bond in GC makes a big difference? Thank you!
You are correct that G-C DNA bond pairs are stronger since they have 3 hydrogen bonds. This is also why DNA strands that are rich in G-C base pairs require higher temperatures to be denatured.
I'm not sure by how much but G-C pair is definitely stronger since, as you mentioned, G-C pair can form 3 hydrogen bonds whereas A-T pair can form only 2. In his lectures, Dr. Lavelle mentioned that the effect of IMFs adds up, and, thus, G-C pairs are more stable.
Yeah so since the G-C pair has 3 hydrogen bonds in comparison to A-T which only has 3, G-C pairs would be considered both stronger and more stable. Also, this would explain why G-C pair bonds need higher temperatures to be denatured.
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