Abstract
Two types of DNA triplexes, intra-and intermolecular triplexes, at polypurine·polipyrimidine segments in both recombinant plasmids and DNA fragments were identified and characterized recently: the former forms in supercoiled plasmids, and the latter forms by combining duplex DNA and a single-stranded oligomer. These findings brought the research on the triplestranded DNA and RNA polymers discoverd 35 years ago into new phase. The possible biological significance of triplexes has been suggested by the fact that polypurine·polypyrimidine sequences are overrepresented in eukaryotic genomes and often are found near genes and recombinational hot-spots. The structural properties and biological implications of DNA triplexes are described.
