By 2003 Illumina scientist Kevin Gunderson invented a chemical process that allowed Illumina to get more-accurate results, even as it packed more DNA on a chip. (Instead of the lithography that Affymetrix uses, Illumina affixes DNA to tiny glass beads packed in the chip.) "I've been in the analytical sciences for 30 years, and I've never seen anything this accurate, " says John W. Hooper, chief executive of Quebec gene-finding firm Genizon, an Illumina customer.

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