What unique ability do DNA molecules have? Why is this ability so important?

Because DNA is a double helix with two chains that are
complementary, either side may act as a template for its replication. DNA is the only
molecule that can copy itself. Its subunits are called nucleotides. These contain a
sugar--deoxyribose, a phosphate group and one of four bases--adenine, guanine, cytosine
or thymine. These bases pair up with their complement on the adjacent chain. The rules
are A pairs with T and C pairs with G. During replication, the hydrogen bonds between
complementary bases are overcome and either chain can be replicated. Free nucleotides
attach to exposed bases. For example, if the DNA code reads:      A, T, C, G, then a
complementary chain will be produced with the basesT, A, G, C. Because of this property,
life can go on. DNA can be replicated for daughter cells produced during mitosis and
also, for gamete production during meiosis.