Mitochondrial DNA
Mitochondrial DNA was discovered in the 1960s by Margit M. K. Nass and Sylvan Nass by electron microscopy as DNase-sensitive threads inside mitochondria, and by Ellen Haslbrunner, Hans Tuppy and Gottfried Schatz by biochemical assays on highly purified mitochondrial fractions.
John E. Walker
From 1969 to 1971, Walker worked at the University of Wisconsin–Madison, and from 1971–1974 in France. He met Fred Sanger in 1974 at a workshop at the University of Cambridge. This resulted in an invitation to work at the Laboratory of Molecular Biology of the Medical Research Council, which became a long-term appointment. Among the other staff was Francis Crick, who was well known for his discovery of the molecular structure of DNA. At first, he analyzed the sequences of proteins and then uncovered details of the modified genetic code in mitochondria. In 1978, he decided to apply protein chemical methods to membrane proteins. In this way, Walker characterized the subunit composition of proteins in the mitochondrial membrane and the DNA sequence of the mitochondrial genome.