Discovery of alternative DNA structures: a heroic decade (1979-1989).

The first alternative DNA structure--left-handed Z-DNA--was described back in 1979. The discoveries of the cruciform DNA structure, three-stranded H-DNA, four-stranded G-quartets and stably unwound DNA followed in the next decade. Each alternative structure was formed by a specific DNA sequence, which as a rule was repetitive. Furthermore, these repetitive elements were situated at functionally important areas of various genomes, pointing to the biological significance of these structures. This chapter concentrates on the first period of studies of alternative DNA structures, beginning in 1979 and ending in 1989, which transformed our views on DNA structure and functioning.