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Unformatted text preview: of 2 nm, 0.34 nm, and 3.4 n. The dark structures at the top and bottom of their X-ray photograph of DNA indicate that DNA contains repeating units, suggesting a helix. James Watson and Francis H.C. Crick, 1953 Watson and Crick used Chargaff's base data and Franklin’s X-ray diffraction data to construct a model of DNA. The model showed that DNA is a double helix with sugar-phosphate backbones on the outside and the paired nucleotide bases on the inside, in a structure that fit the spacing estimates from the X-ray diffraction data. Chargaff's rules showed that A = T and G = C, so there was complementary base pairing of a purine with a pyrimidine, giving the correct width for the helix. The paired bases can occur in any order, giving an overwhelming diversity of sequences....
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This note was uploaded on 11/10/2011 for the course BIOLOGY bi 101 taught by Professor - during the Fall '10 term at Montgomery.
- Fall '10