Answer:
A hydrogen bond is a weak bond formed by the electrostatic attraction that takes place between proton of one molecule and an electronegative atom of another molecule. It can be of two types intra-molecular and inter-molecular.
In water, hydrogen bonds give characteristic properties such as cohesion, high specific heat, high heat of vaporization, a lower density of ice, and solubility.
In DNA, the hydrogen bonds only provide stability to the overall molecule. The two strands of the DNA stay together or remain attached with the help of hydrogen bonds.
The nucleotide base pairs are joined together through hydrogen bonding. The adenine and thymine are joined together with the help of two hydrogen bonds. The cytosine and guanine are joined together with the help of three hydrogen bonds.