Question

DNA strands are anti parallel because of

• A. H-bonds
• B. Phosphodiester bonds
• C. Disulphide bonds
• D. Peptide bonds

Answer 1

Answer: (B)

DNA is double stranded, and the strands are antiparallel because they run in opposite directions. Each DNA molecule has two strands of nucleotides. Each strand has a sugar-phosphate backbone, but the orientation of the sugar molecule is opposite in the two strands. Thus the main reason of this antiparallel nature of the DNA is the presence of a phosphodiester bond that links the phosphate group to the hydroxyl group of the sugar molecule (present in alternate directions on either strand).

So, the correct option is 'phosphodiester bonds'.