Let's say we analysed a nucleic acid and found out that it had 20% adenosine, 25% guanosine, 40% thymidine and 15% cytidine. We know that A always pairs with T and G with C.

So, based on these numbers, could we infer that the nucleic acid must've been single-stranded? Or could it be that it was a double-stranded DNA, but just not perfectly matched? Is it even possible for DNA to not perfectly match? Say like a zipper that is shifted?

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    $\begingroup$ There's 10% of your nucleic acid that's not A, T, G or C - you may have made a major discovery! $\endgroup$ – Harry Vervet Feb 15 '16 at 20:00
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    $\begingroup$ @HarryVervet Haha. Sorry, those were arbitrary numbers. Edited. $\endgroup$ – Phytochrome Feb 15 '16 at 20:02
  • $\begingroup$ Though base pair mismatching is very common and is the basis of evolution, such a big violation of Charagaff's rule (in DNA where just 1% would mean thousands/millions of B.P.s) would only prove that it is ssDNA. $\endgroup$ – another 'Homo sapien' Feb 16 '16 at 15:56
  • $\begingroup$ @aayushsrivastav Awesome! Haven't heard of Charagaff's rule before. That would explain the assumption then. $\endgroup$ – Phytochrome Feb 17 '16 at 8:51
  • $\begingroup$ I'd say it depends on how you 'analyzed it'. You can also have a mixture dsDNA and ssDNA, for instance 20% polyT oligos and 10% polyG oligos. $\endgroup$ – Artem May 20 '17 at 15:29

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