Mitochondria

Abstract

Among the eukaryotes, the function of mitochondria in carrying out oxidative phosphorylation appears highly conserved, and yet the size, organization, and structure of the mitochondrial genome varies enormously (Sederoff 1984). Although most animal mitochondria have a uniformly monomeric circular DNA of about 16 kb, it is the fungal, and even more, the mitochondria of higher plants, which have the bewildering array of size distribution in contained DNA. Thus the size, of mitochondrial genomes in higher plants can vary from approximately 100 kb to as much as 2400 kb, and can be a mixture of linear and circular molecules as well. Advances in this field have been so rapid that some of the properties of mitochondrial DNA can now be used as an analytical tool in detecting, for example, certain types of cytoplasmic male sterility in maize (Pring and Levings 1978). This trait is of major economic importance, being used in the commercial production of hybrids (Duvick 1965). It is maternally inherited and is characterized by easily recognized changes in mitochondrial DNA structure (Schardl et al. 1984). Many other relevations concerning mitochondrial DNA structure and function have followed, so that it now seems that some chloroplast genes are contained also within the corn mitochondrial genome (Lonsdale et al. 1983), and that in yeast at least mitochondrial genes can be found in the nucleus of the cell (Farelly and Butow 1983).