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Homework Help: The Double Helix - Hydrogen bonding and stability

  1. Sep 4, 2010 #1
    Rank the following base pairs according to their stability.
    Rank from most to least stable. To rank items as equivalent, overlap them.


    I have found out that the first one is thymine-adenine pair and the second one is a cytosine-guanine pair. The third one is cytosine paired with adenine, which doesn't make sense, so it must be the least stable. Now how do I go about determining if the A-T pair or C-G pair is more stable? It has something to do with the number of bonds, maybe?
  2. jcsd
  3. Sep 4, 2010 #2
    I think that is a safe assumption. Now just ask yourself which pair would require the most energy to break the hydrogen bonds; G-C with three H-bonds, or A-T with two H-bonds? This will be the most stable pairing.
  4. Sep 4, 2010 #3
    I know that the larger the bond energy, the more energy is needed to break the bond. If the more energy is needed to break the bond, that means the bond is stronger and more stable. Is this correct?
  5. Sep 4, 2010 #4
    Yep. Then just follow mplayer's advice and you should get the answer. I imagine them as being sticky: the more points (bonds) that can stick togeather, the more sticky the molecules are and the harder they are to pull apart!
  6. Sep 4, 2010 #5
    That's a nice trick. Thanks for the advice! :)
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