There are many structures that can be adopted by nucleic acids other than the Watson-Crick duplex. In particular, a noncanonical four-stranded topology, called a G-quadruplex, is of great interest because of its roles in key biological processes such as the maintenance of telomeres and regulation of gene transcription. This review describes the condition for forming the G-quadruplex structure, G-quadruplex-forming sequences, and methods for studying the structures. Curr. Protoc. Nucleic Acid Chem. 40:17.2.1-17.2.17. © 2010 by John Wiley &amp
Sons, Inc. Copyright © 2010 John Wiley &amp
Sons, Inc.