Microarrays, or "gene chips," have become valuable tools for studying changes in gene expression; detecting genetic mutations and polymorphisms; analyzing drug resistance and disease susceptibility; and sequencing unknown DNA. The microarray, which consists of cloned genes, PCR products, or synthetic oligonucleotides immobilized on a microscope slide, is analyzed by hybridization with target DNA or RNA that is labeled with radioisotopes or fluorescent dyes.1 For example, total mRNA isolated from two different cell populations and reverse transcribed into cDNA with two different fluorescent labels can be hybridized with an array of known DNA sequences. The fluorescence for each dye is measured separately to determine the relative abundance of each specific transcript in the two samples.

Unfortunately, many laboratories do not have access to this technology because computer-controlled robots that generate high-density arrays are very expensive. The new MicroCASTer from Schleicher & Schuell Inc. of Keene, N.H., is an economical, 8-pin,...

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