Digital Biology Friday: the answer to last week's puzzle

Last Friday, we had another in the series of weird DNA structures. (You can see the first here). I asked the audience to identify the unusual feature in this molecule. Here's the first picture:

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Here's the answer: Steve L. guessed it correctly. This is not just DNA, it's a DNA:RNA hybrid. I circled a 2' hydroxyl group here to make it easier to see the difference. (Remember - the "D" in DNA stands for "deoxy.") The oxygens are red and it's easiest to tell the difference between the strands if you count them. For extra credit - where might you find this kind of thing in nature?