The Invader assay technology is Third Wave Technologies' (Madison, Wis.) isothermal, "PCR-free" approach to the detection and quantitative analysis of DNA. Instead of amplifying the target of interest, and thereby increasing the chances of "carryover" contamination, the Invader assay produces and amplifies an unrelated signal only in the presence of the correct target sequence.1 These incredibly sensitive assays can be harnessed to quantify subattomole levels of target nucleic acids within complex mixtures, and can also be used to detect genetic mutations or single nucleotide polymorphisms (SNPs) directly from genomic DNA, without the need for prior amplification of the target sequence. This technology exploits a thermostable member of the structure-specific archaebacterial flap endonuclease (FEN) family.2 These enzymes cleave nucleic acid molecules at specific sites based on structure rather than sequence. When used in conjunction with structure-forming probes for known sequences, the enzymes cleave in a structure- and target sequence-specific...

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