Given below are two statements. How many of the following statements are correct ?
Statement I: Watson and Francis Crick, proposed a double helix model for the structure of DNA based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin
Statement II: This proposition was also based on the observation of Erwin Chargaff that for a double-stranded DNA, the ratios between adenine and thymine and guanine and cytosine are constant and equals one.
In light of the above statements, choose the most appropriate answer from the options given below.

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Statement I is correct, but statement II is incorrect.

Statement I is incorrect, but statement II is correct.

Both statement I and statement II are correct.

Statement I and statement II are incorrect.

answer is D.

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Detailed Solution

Watson and Crick proposed the double helical model of DNA based on the physical evidence provided by Maurice Wilkins and Rosalind Franklin and the chemical analysis data provided by Erwin Chargaff that for a double stranded DNA, the ratios between Adenine and Thymine and Guanine and Cytosine are constant and equals one.
The model relies on the base pairing rule which confers a very unique property to the polynucleotide chains, complementarity.
Adenine always base pairs with thymine and guanine always base pairs with cytosine.as a result the amount of guanine always equals the amount of cytosine and the amount of adenine always equals to the amount of thymine
Chargaff proposed two rules applicable for ds DNA .
a) The amount of purine = to amount of pyrimidine A+G/T+C is always constant and equals 1 . b) The ratio of A +T to G+C is unequal, It varies from species to species.

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