As a result, it can get highly accurate results in 90 minutes.

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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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Furthermore, the lack of a rival provider of tests to get a second opinion makes it impossible to ensure that results are accurate.

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