DNA denaturation (C paired with G) - biochem/bio

[yestomeds]

Hey everyone, this is a super simple question.

THIS IS FACTUAL. I UNDERSTAND THIS PART:
So C forms a triple hydrogen bond with G, hence when the DNA ds is rich with CG pairing, it'll require higher temperatures to denature (i.e. the double stranded DNA will then denature at a higher temperature than would an AT rich double strand of DNA).

AND THIS IS MY QUESTION:
So why would a SINGLE STRAND formed of lots of Cs and Gs require higher temperatures to denature? (i.e. the base composition on this single strand is mostly be made of C and G).
Saying this implies that something inherently within the C or G dNTPs makes them require higher heat. BUT I thought the whole point behind Cs and Gs requiring higher temperatures to denature was the HYDROGEN BONDING occurring between them i.e. necessitating that they be double stranded, and not single stranded like what the question/answer was about!

If you're confused by my question, this is from an old EK passage - EK 1001's, chapter 2, passage 204 (page 27), question #147, with answers on p. 198. Thanks a ton.

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[Quinoline]

I'm pretty sure the question is asking about double stranded DNA, the answer key discusses H bonding like you did. I do believe though that G/C does have a slightly higher molecular weight.

 

[bee17]

Hmmmm. Well, single-stranded nucleic acids are certainly capable of folding over and base-pairing with themselves to form 3D structure (example: tRNA, hairpins). We usually talk about it with RNA, but DNA can do it too.

 

[StIGMA]

Hmmmm. Well, single-stranded nucleic acids are certainly capable of folding over and base-pairing with themselves to form 3D structure (example: tRNA, hairpins). We usually talk about it with RNA, but DNA can do it too.

This is what the question is referring to. A single stranded structure (DNA/RNA) in solution will form the lowest-energy structure possible (as will any molecule). This means a single stranded DNA will in-fold onto itself, with G-C and A-T pairings (with some bases going unpaired based on the 3D structure [drawn as 2D structure, examples below). The energy between each pair is similar to a double-stranded pairing because the hydrogen bonding is exactly the same (a long stretch of folded/bonded single stranded DNA looks exactly like dsDNA).

eg:

 

[yestomeds]

Thanks! You're saying that yes, I wasn't going crazy in interpreting that the question/answers WERE talking about ss DNA.
But also that implicit in all this was the understanding that the given ss DNA WOULD FOLD ONTO ITSELF i.e. "behave" sort of like a ds DNA. In which case its GC content would up the temp needed to denature?!

Thanks @StIGMA and everyone!

 

[chemist16]

If the single-stranded DNA didn't fold over on itself and create substructures like that, there would be no need to denature it in the first place. Denaturation in that sense is meaningless.