Solution:
Salient features of double helix structure of DNA:
- There are two polynucleotide chains in double stranded DNA.
- Backbone is constituted by sugar phosphate.
- Two strands possess antiparallel polarity means one chain has polarity 5’-3’ and the other has 3’-5’.
- Two strands of DNA are joined together by hydrogen bonds between purines and pyrimidines.
- Adenine always pairs with Thymine by two hydrogen bonds.
- Guanine always pairs with Cytosine by three hydrogen bonds.
- Backbone of the DNA double helix is formed by sugars and phosphates where bases are projecting inwards.