A form of DNA duplex in which the double helix is wound in a left-hand, instead of a right-hand, manner. DNA adopts the Z configuration when purines and pyrimidines alternate on a single strand, e.g.,

5´CGCGCGCG3´ or 5´CACACACACA3´

3´GCGCGCGC5´ 3´GTGTGTGTGT5´