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Obtained X-ray diffraction analysis data of highly purified DNA samples
Confirmed the 3.4Å measurement between the stacked nucleotide bases as well as the structure being some kind of helix (Astbury originally proposed this) |
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separated nucleotides from DNA samples from multiple species and measured the amount of each base present.
Amount of adenine≈amount of thymine
Amount of cytosine≈amount of guanine
BUT the percent of A+T was not equal to the percent of C+G present AND these amount varied from species to species.
Disproved the previous repeating tetranucleotide hypothesis (all nucleotides follow a single pattern that repeats but in different amounts for each species) |
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| Used the discoveries of Franklin/Wilkins, Chargaff and others to build the Watson and Crick model of the DNA molecule. |
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-DNA is a double helix made of antiparallel* polynucleotide chains on a sugar phosphate backbone coiled around a central axis.
-Bases are perpendicular to the axis and stacked parallel to one another 3.4Å apart
-The base pairs are A-T and G-C which are hydrogen bonded
-A full turn is 34Å long (10 bases in each turn)
-There are alternating major (22Å) and minor (12Å) grooves in the chains
-The diameter is 20Å
*antiparallel: one chain is 3' to 5' while the other is 5' to 3'. |
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