During DNA replication, the hydrogen bonds must be broken between the complementary nitrogenous bases in the DNA double helix. Once this is accomplished, either side of the DNA molecule can act as a template to produce another double stranded DNA molecule. Free nucleotides(units of DNA) which contain a nitrogenous base, will pair up with their complementary base on the DNA molecule. The base pairing rules are adenine pairs with thymine and cytosine pairs with guanine. Eventually, each half of the DNA molecule will be replicated and two complete double helixes will be the end result.
it is broken between COMPLEMENTORY nitrogenous bases in DNA.