sequence_secondary_structure
G_quartet
http://en.wikipedia.org/wiki/G-quadruplex
sequence
G quartet
SO:0000003
G-quadruplex
G-quartet
guanine tetrad
G tetrad
G_quadruplex
G-quartets are unusual nucleic acid structures consisting of a planar arrangement where each guanine is hydrogen bonded by hoogsteen pairing to another guanine in the quartet.
G-tetrad