The model of the DNA can be related to a zipper. Just like the zipper, the two strands of the DNA are joined together by the hydrogen bonds present between the nucleotides. At the time of replication, the coiling of the two strands is undone just as the zipper is open. The two strands of the DNA open and separate just as the two stands of the zipper open and separate. Each strand can give rise to anew strand.
Just as the opening and closing of the zipper can cause damages in the zipper, just like this replication can cause errors in the DNA which lead to mutations.
