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Which of the following statements with respect to the orientation of the nitrogenous bases to the pentose sugars, and the puckering of the sugar, is correct?
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- Anti, and 2’-endo in A form DNA
- Anti, and 2’-endo in B form DNA
- Syn, and 3’-endo in A form DNA
- Syn, and 3’ -endo in B form DNA
Correct Option: B
Nitrogenous bases are always arranged in "anti" positions to their corresponding pentose sugar moieties. In B-form of DNA, sugar puckering occurs predominantly in the C2 position of the pentose sugar. The sugar pucker determines the shape of the a-helix, whether the helix will exist in the A-form or in the B-form. So, in C2-endo puckering occurs in B-form of DNA.
