Many small gaps remain, and these complicate still further the job of identifying genes by looking directly at the sequence of base pairs.

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For an era of targeted therapies, Private Health runs a full battery of molecular diagnostics "to sequence the entire three billion base pairs of somebody's DNA in a couple of hours, " Mr. Michelson marvels.

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Last week, Celera announced it had delivered 1.2 billion base pairs of the humane genome sequence to its subscribers.

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And some parts, particularly those where the same short pattern of base pairs is repeated over and over again, remain difficult to sequence well.

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