Hydrogen Bonding and Stability of the Double Helix

The four bases in DNA are complimentary in nature. In its double helical structure the bases from each strand project inwards towards each other.
Each base from one strand is bound to the other base from the other strand through hydrogen bonding interactions.
This interaction stabilizes the double helix. Adenine is always hydrogen bonded to Thymine and Guanine to cytosine.
If the sequence of bases in one strand is known the sequence in the other strand is predictable.
There are two points of hydrogen bonding between Adenine and Thymine and three between Guanine and Cytosine.

Features of Hydrogen Bonding