Separation of heteroduplexes by polyacrylamide gel electrophoresis.

<p>Southern blot of artificial heteroduplexes, made by melting and reannealing the 604 bp long DNA fragment with and without an 18 bp insertion marker, run on a 5% polyacrylamide gel. (A) Hybridization of the blot with a PCR-labeled probe complementary to the entire 604 bp restriction fragment. (B) Hybridization with an oligo probe complementary to the loop sequence in the strand ending 5′ at the right. (C) Hybridization with an oligo probe complementary to the loop sequence in the 3′-ending strand. “+”, the homoduplex fragment containing the 18 bp insert; “-”, the homoduplex fragment with no insert; “mixed”, melted and reannealed “+” and “−” DNAs (artificially prepared heteroduplexes). Figures beneath the gels represent the structures of Homo- and Het-containing fragments, showing the sequences of the complementary loops. “Het”, heteroduplex; “Homo”, homoduplex.