Question

Write any four salient features of the Double helix structure of DNA.

Answer 1

The salient features of double helix structure of DNA are as follows:

• There are two polynucleotide chains in a double stranded DNA.
  
• The backbone is constituted by sugar phosphate.
  
• The two strands possess anti-parallel polarity, means one chain has polarity 5’-3’ and the other has 3’-5’.
  
• The two strands of DNA are joined together by hydrogen bonds between purines and pyrimidines.
  
• Adenine always pairs with Thymine by two hydrogen bonds and Guanine always pairs with Cytosine by three hydrogen bonds.
  
• The two chains are coiled around each other where the pitch of the helix is 3.4 nm and distance between two base pairs is 3.4 A° (as in case of B-DNA)
  
• The backbone of DNA double helix is formed by sugars and phosphates where bases are projecting inwards.