Scientists how to prove DNA is anti-parallel?


closed as off-topic by canadianer, David, John, Bryan Krause, AliceD Oct 16 '18 at 7:26

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework questions are off-topic on Biology unless you have shown your attempt at an answer. For more information see our homework policy." – David, John, Bryan Krause, AliceD
If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Hello and welcome to Bio.SE! Take the tour to learn about the site and earn yourself your first badge. Also, we require questions to show the previous efforts looking for an answer. What did you already do in order to find experiments for anti-parallel DNA? $\endgroup$ – LinuxBlanket Oct 12 '18 at 6:38
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    $\begingroup$ @LinuxBlanket i still think thats only homowork. :) $\endgroup$ – L.Diago Oct 12 '18 at 7:00
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    $\begingroup$ @L.Diago I know, but let's know them the site policy :) $\endgroup$ – LinuxBlanket Oct 12 '18 at 7:09

The definitive proof came with the crystal structure of B-DNA (see Watson & Crick, 1953). Anti-parallel strands is the configuration that best explained the diffraction data while not violating chemistry (bond lengths and angles, no steric clashes, etc.).

The relevant sentence from the article is:

the sequences of the atoms in the two chains run in opposite directions

I underlined this sentence in the following screenshot of the article:

DNA structure

  • $\begingroup$ Why are you answering homework questions that clearly do not satisfy SE Biology criteria as two comments make clear. Doing so encourages cheats and people too idle to do any research of their own. $\endgroup$ – David Oct 12 '18 at 22:44
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    $\begingroup$ Because I am not convinced it's a homework question. Assuming it is a homework question, it's a poorly formulated one anyway because the article containing the answer is behind a paywall, even on campus at a US university (I just checked where I work), which means no student would realistically find the answer on their own easily. $\endgroup$ – Guillaume Oct 12 '18 at 23:18
  • $\begingroup$ Whether or not you think the question was homework, @LinuxBLanket had explained the deficiency of the question. It is reasonable to expect the OP to respond this (and the comment about home work), and to wait until he has done so before answering. As for the unavailability of the original Watson and Crick paper, this is described in every book on biology, and is available on line in a far more comprehensible form to the student. I would wait until there is a request for access to original sources before posting, and then do so in a form that does not discriminate against the partially sighted. $\endgroup$ – David Oct 13 '18 at 13:29
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    $\begingroup$ You're right about accessibility: I should have retyped the sentence instead of posting a screenshot (the PDF is a scan from which I couldn't copy text, and I was lazy, hence the screenshot). Will edit the answer accordingly. Now, I disagree with the rest of your comment: answers on SE are public and therefore potentially useful to anybody (not only the OP), who would never find the information because it's behind a paywall. $\endgroup$ – Guillaume Oct 14 '18 at 3:45
  • $\begingroup$ I am not sure that I would agree that Watson and Crick's paper provided the 'definitive proof' that the strands are anti-parallel. Their structure of DNA was (and is) after all a model, and could have been wrong on this point. The OP is looking for the experimental evidence that confirms the assersion that the strands are anti-parallel, in the same way that Meselson & Stahl provided unequivocal experimental evidence that replication is semi-conservative. As Brändén and Jones' put it, "crystallographic interpretation remains to some extent subjective” $\endgroup$ – user1136 Oct 14 '18 at 15:00

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