DNA sequencing by hybridization--a megasequencing method and a diagnostic tool?

The length of DNA from different sources that has been sequenced has already exceeded 1 x 10(8) bases, and this figure is continuing to grow exponentially. Even so, the very large quantity of DNA that remains to be sequenced and the impetus generated by the worldwide Human Genome Project has increased the need for the development of megasequencing procedures. Sequencing by hybridization (SbH) shows promise as an approach for developing such a method. The technique involves hybridization of the DNA of unknown sequence with an enormous set of short oligonucleotides; identification and analysis of the overlapping set of oligomers that form perfect duplexes with the DNA of interest permits reconstruction of the target-DNA sequence. Preliminary experiments have already demonstrated the feasibility of incorporating this approach into large-scale sequencing projects, and processes have been developed both for manufacturing the sequencing microchips that incorporate the immobilized oligonucleotides, and for detecting hybridization of the target DNA to these microchips.