http://www.lifemapdna.com/explain-why-the-double-helix-structure-of-dna-allows-only-a-purine-to-pair-with-a-pyrimidine.html Thu, 08 Sep 2011 20:10:50 +0000 http://wordpress.org/?v=2.9.2 hourly 1 http://www.lifemapdna.com/explain-why-the-double-helix-structure-of-dna-allows-only-a-purine-to-pair-with-a-pyrimidine.html/comment-page-1#comment-1295 emucompboy Sun, 15 Nov 2009 19:21:03 +0000 http://www.lifemapdna.com/explain-why-the-double-helix-structure-of-dna-allows-only-a-purine-to-pair-with-a-pyrimidine.html#comment-1295 When Crick eyeballed Franklin's x-ray diffraction image of DNA, he noticed that the picture implied a constant width and regular repeating pattern for the molecule. Constant width, with base pairing, implies that a purine must pair with a pyrimidine, and never with another purine; similarly a pyrimidine can't pair with another pyrimidine. These guys are different "widths." When Crick eyeballed Franklin’s x-ray diffraction image of DNA, he noticed that the picture implied a constant width and regular repeating pattern for the molecule.
Constant width, with base pairing, implies that a purine must pair with a pyrimidine, and never with another purine; similarly a pyrimidine can’t pair with another pyrimidine. These guys are different "widths."

]]> http://www.lifemapdna.com/explain-why-the-double-helix-structure-of-dna-allows-only-a-purine-to-pair-with-a-pyrimidine.html/comment-page-1#comment-1296 damnhippies50 Sun, 15 Nov 2009 19:21:03 +0000 http://www.lifemapdna.com/explain-why-the-double-helix-structure-of-dna-allows-only-a-purine-to-pair-with-a-pyrimidine.html#comment-1296 G to C has three hydrogen bonds, and A to T has two hydrogen bonds so they cannot mismatch G to C has three hydrogen bonds, and A to T has two hydrogen bonds so they cannot mismatch

]]> http://www.lifemapdna.com/explain-why-the-double-helix-structure-of-dna-allows-only-a-purine-to-pair-with-a-pyrimidine.html/comment-page-1#comment-1297 tapoona Sun, 15 Nov 2009 19:21:03 +0000 http://www.lifemapdna.com/explain-why-the-double-helix-structure-of-dna-allows-only-a-purine-to-pair-with-a-pyrimidine.html#comment-1297 purines are A and G and pyrimidines are C and T. Just like the other answer said they pair up because of the number of bonds, but it doesn't have to do with being a purine or pyrimidine. a good way to remember that A and G are purines is the pneumonic "Pure silver." Purines are A and G or Ag (silver). purines are A and G and pyrimidines are C and T. Just like the other answer said they pair up because of the number of bonds, but it doesn’t have to do with being a purine or pyrimidine. a good way to remember that A and G are purines is the pneumonic "Pure silver." Purines are A and G or Ag (silver).

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