microchips using this technique one can determine the presence of mutations or even sequence the nucleic acid being analyzed or one can measure expression levels of a gene of interest the method is one of parallel processing of many even thousands of probes at once and can tremendously increase the rate of analysis several papers have been published which use this technique some of these are hacia et al 1996 shoemaker et al 1996 chee et al 1996 lockhart et al 1996 derisi et al 1996 lipshutz et al 1995 this method has already been used to screen people for mutations in the breast cancer gene brca1 hacia et al 1996 this new technology has been reviewed in a news article in chemical and engineering news borman 1996 and been the subject of an editorial editorial nature genetics 1996 also see fodor 1997 the most definitive test for mutations in a candidate locus is to directly compare genomic kvlqt1 herg scn5a kcne1 or kcne2 sequences from patients with those from a control population alternatively one could sequence messenger rna after amplification e g by pcr thereby eliminating the necessity of determining the exon structure of the candidate gene mutations from patients falling outside the coding region of kvlqt1 herg scn5a kcne1 or kcne2 can be detected by examining the non coding regions.