Edward B. Lewis

Edward B. Lewis (May 20, 1918 – July 21, 2004) was an American geneticist. He shared the 1995 Nobel Prize in Physiology or Medicine.
Lewis was born in Wilkes-Barre, Pennsylvania He received a BA in Biostatistics from the University of Minnesota in 1939.
In 1942 Lewis received a PhD from California Institute of Technology (Caltech), working on "Drosophila melanogaster" under the guidance of Alfred Sturtevant.
After serving as a meteorologist in the U.S. Air Force in World War II, Lewis joined the Caltech faculty in 1946 as an instructor. In 1956 he was appointed Professor of Biology, and in 1966 the Thomas Hunt Morgan Professor of Biology.
His Nobel Prize winning studies with "Drosophila" founded the field of developmental genetics and laid the groundwork for our current understanding of the universal, evolutionarily conserved strategies controlling animal development.
His key publications in the fields of genetics, developmental biology, radiation and cancer are available in a book.
Effects of radiation.
During the 1950s, Lewis studied the effects of radiation from X-rays, nuclear fallout and other sources as possible causes of cancer. He reviewed medical records from survivors of the atomic bombings of Hiroshima and Nagasaki, as well as radiologists and patients exposed to X-rays. Lewis concluded that "health risks from radiation had been underestimated". Lewis published articles in "Science" and other journals and made a presentation to a Congressional committee on atomic energy in 1957.
At the scientific level of the debate, the crucial question was whether the "threshold theory" was valid or whether, as Lewis insisted, the effects of radioactivity were "linear with no threshold", where every exposure to radiation had a long-term cumulative effect.
Genes regulating development.
In a series of experiments with the fruit-fly "Drosophila", Lewis was able to identify a complex of genes whose proteins bind to the regulatory regions of target genes. The latter then activate or repress cell processes which direct the final development of the organism.
The sequence of these control genes show "co-linearity": the order of the loci in the chromosome parallels the order in which the loci are expressed in segments along the body. Not only that, but this cluster of master control genes programs the development of all higher organisms.
Each of the genes contains a homeobox, a remarkably conserved DNA sequence. This suggests the complex itself arose by gene duplication.
In his Nobel lecture, Lewis said "Ultimately, comparisons of the [control complexes] throughout the animal kingdom should provide a picture of how the organisms, as well as the [control genes] have evolved".