Hood , Leroy Edward

(1938–) American biologist

Born in Missoula, Montana, Hood was educated at the California Institute of Technology, where he obtained his PhD in biochemistry in 1964, and at Johns Hopkins Medical School, Baltimore, where he qualified as an MD in 1964. He immediately joined the staff of the National Institute of Health, Bethesda, working in the area of immunology. In 1970 Hood returned to the California Institute of Technology and was appointed professor of biology in 1975.

In May 1985 at a meeting in Santa Cruz, California, plans were laid to map the human genome (the Human Genome Project). As the genome consists of 3 billion base pairs of DNA, the ability to sequence the genes rapidly would be a crucial factor.

Fortunately an automatic sequencer was almost at hand in 1985, developed by Hood and his colleague Lloyd Smith. The sequencer operates with fluorescent dyes. Each of the four DNA bases – adenine (A), cytosine (C), guanine (G), and thymine (T) – can be tagged with a different dye. Unsequenced dye-tagged DNA fragments are analyzed by gel electrophoresis, in which they migrate at different rates. The dyes are excited by an argon laser and the light emitted is turned into a digital signal by photomultiplier tubes. The digital signals can be analyzed by a computer and identified as A, T, C, or G.

Hood's automatic sequencer enabled work that once took a week or more to be carried out overnight. Later commercial models of the device can read 12,000 base pairs a day, and operate more accurately than any manual sequencing.

In 1992 Bill Gates of Microsoft presented the University of Washington Medical School, Seattle, with $12 million to establish a department of molecular biotechnology. Hood was persuaded to move to Seattle to head the new department, to work on a faster DNA sequencer, and to analyze the genes controlling the human immune response. That same year Hood, in collaboration with Ronald Cape, a former head of the biotechnology firm Cetus, founded Darwin Molecular in Seattle. Their aim is to develop new drugs utilizing processes comparable to natural selection.