He was 84.

The California Institute of Technology said Attardi was a leading figure in identifying the products and functions of the mitochondrial genome.

Attadi was born in Italy in 1923 and came to the United States on a Fulbright Fellowship, arriving at Caltech in 1959. He was appointed associate professor of molecular biology in 1963, the university said in a release.

"Giuseppe was one of the founders of what is now a central and still-expanding area of molecular cell biology," Gottfried Schatz, emeritus professor of biochemistry at the University of Basel's Biozentrum in Switzerland, said in a statement. "His unique insights bore magnificent fruits with the landmark description of the transcription map of mammalian mtDNA, as well as the precise characterization of the mechanism of mitochondrial diseases and the dynamics of human mitochondrial genomes."