The 16569 base pairs of the mitochondrial DNA encode with a specific genetic 
code 13 proteins involved in the respiratory chain complex formation. Nuclear 
gene products also contribute to the formation of these complexes. In the first 
point, the organization and expression of the mtDNA are described with the main 
characteristics of the enzymatic complexes as well as nuclear gene expression. 
New information concerned with mitochondrial DNA deletions and mutations are 
described particularly with respect to Kearns-Sayre Syndrome.