In the past few years, the body of experimental work on the structure, function and assembly processes of mitochondria has expanded rapidly. No one person can believe himself or herself completely in control of the burgeoning literature without possessing serious omissions or blind spots. In the present monograph I have attempted a critical evaluation of the literature. I believe that the common thread of single authorship outweighs the shortcomings of one person presenting many disparate viewpo,ints. It is my hope that the end product represents a comprehensive and coordinated review of the subject matter to the present date. Although the bulk of this monograph was completed by October 1974, I have made some attempts to update several of the sections at later times. Albany, N. Y. , November 1975 H. TEDESCHI Contents A. Structure of Mitochondria 1. General Organization . a) Conventional Thin Section Electron Microscopy b) Negative Staining Techniques . 3 c) Freeze-Cleavage . . . . . . . 4 2. Special Organization and Inclusions 10 a) Prismatic or Atypical Cristae 10 b) Filaments and Tubules . . 11 c) Amorphous Inclusions 12 d) Intramitochondrial Granules 12 e) DNA Containing Fibers 14 3. Topography of the Mitochondrial Transducing Systems 15 B. The Assembly of Mitochondria 18 1. Mitochondrial DNA and Its Genetic Role 19 2. Transcription of the Mitochondrial DNA . 28 a) mRNA . . . . . . . . . . . . . . 30 b) The Machinery for Transcription and Translation 32 c) Turnover of Mitochondrial RNA 36 3. Protein Synthesis . . . . . . . . 37 a) Mitochondrial Protein Synthesis and Its Characteristics 37 b) Role of Mitochondrial Protein Synthesis . .