How do you compare a DNA molecule to a zipper?
DNA or deoxyribonucleic acid molecule is a double stranded molecule, that is, there are two legs or chains of this molecule. The strands are complementary to each other and are connected together by interlinking. The interlinking is provided by base pairing (adenosine (A) with thymine (T) and cytosine (C) with guanine (G)). The two sides have to fit well with each other (through base pairing) for the molecule to work.
Similarly, the zipper (on our bags, trousers, clothing, sleeping bags, etc.) has two strands or two legs. These two strands are complementary to each other and are interlinked to close the zip. The 'teeth' on one side of the zipper fits well into the open space between tooth on the other side of the zipper. The zipper is closed by moving the slider. The zipper's utility is because we can close it.
Hence DNA and zipper are similar to each other in a number of ways.
hope this helps.