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?