While James Watson and Francis Crick were trying to determine the structure of D

Question

While James Watson and Francis Crick were trying to determine the structure of DNA, Linus Pauling published his thoughts about the molecular arrangement (Pauling and Corey, 1953). He placed the phosphates at the interior of the helix, with the bases facing outward (probably so that the information was accessible to the cellular machinery). Give two reasons why this arrangement is unsatisfactory in light of what we now know. Hint: Think about the evidence Watson and Crick needed to determine the structure of DNA

Explanation / Answer

watson and crick needed evidence of three dimentional double helical structure of DNA. they discover the structure of DNA by X ray crystrallography and it is somehow looks like "X". because the the outward phosphate backbone is attached with the antiparellel strand with the inward DNA bases. these bases are attached with the antiparellele strand with hydrogen bond. additionally the double helix is spiral, which gives it a "X" like arrangment in X ray crystrallography.

so the arrangment what pauling and corey describe (phosphate that interior to helix and bases facing outward), has no similarities with watson and crick model.because if the bases facing the outward direction, than it not looks like what observed in watson and crick's experiment. hence the assumption what pauling and corey made was wrong.

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