DNA contains more than one form of bond.
One of these is Hydrogen bonds. These aren't really bonds but interactions between a hydrogen atom attached to an electronegative atom, and an electronegative atom which has a lone pair of electrons. If this atom is a first row element, the bond is especially strong.
Hydrogen bonding between nucleotides is what holds together the two antiparallel strands of DNA.
In DNA these electronegative atoms are either oxygen or nitrogen, thus the bonds are strong.
Two hydrogen bonds join adenine to thymine while three link cytosine to guanine.
The hydrogen bonds are resposible for the double-helical structure of DNA.
Another type of bond present in DNA is the glycosidic bond This refers to the nitrogen-carbon linkage between the 9' nitrogen of purine bases or 1' nitrogen of pyrimidine bases and the 1' carbon of the sugar group.
Also the ester bond, ie the oxygen-carbon linkage between the triphosphate group and the 5' carbon of the ribose sugar group in a single DNA or RNA nucleotide.