Lee Hood did that rarest of things. He enabled scientists to see things they couldn't see before and do things they hadn't dreamed of doing. Scientists can now sequence complete human genomes in a day, setting in motion a revolution that is personalizing medicine.

Hood, a son of the American West, was an unlikely candidate to transform biology. But with ferocious drive, he led a team at Caltech that developed the automated DNA sequencer, the tool that paved the way for the Human Genome Project. He captivated scientists with his almost religious fervor for the new biology enabled by...