Question

The purine & pyrimidine pairs of complementry strands of DNA are held together by

• A. H bonds
• B. O bonds
• C. C bonds
• D. N bonds

Answer 1

The correct option is A H bonds

The purine & pyrimidine pairs of complementry strands of DNA are held together by hydrogen bonds. A set of five nitrogenous bases is used in the construction of nucleotides, which in turn build up the nucleic acids like DNA and RNA.

These nitrogenous bases are adenine (A), guanine (G), thymine (T), and cytosine (C) and uracil (U - in RNA replacing thymine). These nitrogenous bases have hydrogen bond between opposing DNA strands to form the rungs of the "twisted ladder" or double helix of DNA or a biological catalyst that is found in the nucleotides. Adenine is always paired with thymine, and guanine is always paired with cytosine. These are known as base pairs.