Parallel DNA: generation of a duplex between two Drosophila sequences in vitro.

We have observed the existence of a parallel complementary region between two Drosophila DNA sequences, fragments of the suffix [(1986) EMBO J, 5, 2341-2347] and a 5'-non-coding sequence of the alcohol dehydrogenase gene [(1983) Cell 33, 125-133]. The region includes approximately 40 bp, 76% of which are complementary in the same polarity. Synthetic complementary 16 bp oligonucleotides corresponding to this region which were bound by the 5'-ends through a 1.6-hexanediol bridge form a duplex which displays both melting and annealing as judged by UV absorbance. Anti parallel complementary 16 bp long oligonucleotides bound by the 5'-3' ends through the same bridge and a single-strand sequence were used as controls. The Hoechst 33,258 drug binds to this parallel duplex of DNA; however, the properties of such a complex testify against the B-form of the duplex.