Figure 1.

Steps in the microsphere-based invasive cleavage assay. Gray lines represent probe oligonucleotides, which are labeled with fluorescein (F) and a dabcyl quencher moiety (Q). Striped lines represent upstream oligonucleotides. Both types of oligonucleotide are tethered to the microsphere surface by a long linker, represented in the figure by a black lollipop shape. Genomic DNA hybridizes to the probe and upstream oligonucleotides to form a tripartite substrate, as shown in the inset box. When the probe is complementary to the genomic DNA at the position of the SNP the enzyme cleaves the probe, releasing the quencher. In the figure, fluorescence of fluorescein molecules on cleaved probes is represented by an F highlighted by a starburst.