Which type of chemical bond maintains the pairing of each chain in the DNA molecule?
To produce the DNA molecule, purine bases bind to pyrimidine bases by intermolecular bonds called hydrogen bonds. Hydrogen bonds happen when there is hydrogen near one of these electronegative elements: fluorine, oxygen or nitrogen.
In such conditions hydrogen looks like having lost electrons for those elements and a very strong polarization is formed. The highly positive hydrogen attracts pairs of electrons of other molecules making a hydrogen bond.