How It Works: CGH Arrays

Comparative genomic hybridization (CHG) provides the densest coverage of probes for CNV detection, but the traditional technique using bacterial artificial chromosome arrays is time consuming and not always reproducible. Two companies, Agilent and NimbleGen, have released dedicated CGH platforms that instead use oligonucleotide probes; both provide flexibility in the way they design probes. Agilent's platform relies on laser-printing technology, while NimbleGen's system is built around a Digital Micromirror Device (DMD) made by Texas Instruments, similar to the technology in digital projectors. The DMD's micromirrors reflect a specific pattern of light into a synthesis chamber, essentially creating changeable "virtual masks" -- micromirrors set to "off" prevent oligo synthesis at a specific feature, and those flipped "on" allow synthesis to proceed.