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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Abhijeet Gaurav
The correct answer is option (C). The Structural variations in DNA reflects 3 things : a) different possible conformation of deoxyriboses b) rotation about contiguous bond that make up Phosphodiester bond backbone c) free rotation about C1 - N- glycosyl bond. The conformation of nucleotide of DNA is affected by rotation about 7 diff bonds. 6 bonds rotate freely & limited rotation about Bond 4 give rises to Ring Pucker. In which one of the atom of furanose Ring is out of pland described by other 4. This conformation is Endo or Exo depending on whether atom is displaced to the same side of plane or opposite side of C5. For Purine bases only 2 conformation with Respecte to attached ribose units are permitted Syn or Anti. Pyrimidine bases generally occur in Anti Conformation.