amplification followed by base-extension sequencing with pyrophosphate detection in an array of wells. Both groups read about the same amount of sequence, 30 million base pairs, in each sequencing run. Our system read about 400 base pairs a second, whereas 454 read 1,700 a second. Sequencing usually involves performing multiple runs to produce a more accurate consensus sequence. With 43-times coverage (43×)—that is,