John R. Roth is a Distinguished Professor of Biological Sciences at the University of California, Davis

University of California, Davis

The University of California, Davis is a public teaching and research university established in 1905 and located in Davis, California, USA. Spanning over , the campus is the largest within the University of California system and third largest by enrollment...

. He became known for his early studies on the structure and regulation of the his

Histidine

Histidine Histidine, an essential amino acid, has a positively charged imidazole functional group. It is one of the 22 proteinogenic amino acids. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans...

operon of Salmonella

Salmonella

Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...

, and went on to investigate regulation in systems as diverse as suppression by tRNA, NAD

Nicotinamide adenine dinucleotide

Nicotinamide adenine dinucleotide, abbreviated NAD, is a coenzyme found in all living cells. The compound is a dinucleotide, since it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine base and the other nicotinamide.In metabolism, NAD is involved...

 biosynthesis, and the Vitamin B12

Vitamin B12

Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...

-dependent metabolism of small molecules such as ethanolamine

Ethanolamine

Ethanolamine, also called 2-aminoethanol or monoethanolamine , is an organic chemical compound that is both a primary amine and a primary alcohol . Like other amines, monoethanolamine acts as a weak base...

 and propanediol

Propanediol

Propanediol may refer to either of two isomeric organic chemical compounds:*1,2-Propanediol *1,3-Propanediol...

. In collaboration with David Botstein and Nancy Kleckner, he developed the use of transposons as genetic tools. As a by-product of his study of transposons, he developed an interest in chromosomal duplications, which are frequent in bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

. He has recently authored several papers on the involvement of such small-effect mutations on evolution under selection

Selection

In the context of evolution, certain traits or alleles of genes segregating within a population may be subject to selection. Under selection, individuals with advantageous or "adaptive" traits tend to be more successful than their peers reproductively—meaning they contribute more offspring to the...

. In 1988, he became a member of the National Academy of Sciences

United States National Academy of Sciences

The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...

, and in 2009 was awarded the Thomas Hunt Morgan Medal

Thomas Hunt Morgan Medal

The Thomas Hunt Morgan Medal is a medal awarded for lifetime contributions to the field of genetics. The medal is awarded by the Genetics Society of America.-Award recipients:* 1981 Barbara McClintock and Marcus M. Rhoades* 1982 Sewall Wright...

 of the Genetics Society of America

Genetics Society of America

The Genetics Society of America is a scholarly membership society of more than 4000 genetics researchers and educators, established in 1931...

.