I will discuss several aspects of the eukaryotic origin of mitochondria in the various subpages. At this moment, I have entries on:
-Circular and linear mitochondrial genomes including their origin. Interconversion between linear and circular genome is quite common and acquisition of genes from the nuclear genome seems feasible, either in linear or circularized form. See here.
-Early true mitochondria with the oxidative phosphorylation machinery. Many mitochondrial genomes have only a couple of genes or even no genes at all, in line with a gradual acquisition of DNA and an original nuclear control of the metabolic processes. See here.
-Intermediate forms in the gradual evolution towards mitochondria. Various amitochondriate organisms exist that have no genome or a very small genome and that contain putative (anaerobic) precursors to mitochondrial metabolism. See here.
-Protein targeting in mitochondria and putative intermediates. It is clear that mitosomal, hydrogenosomal and mitochondrial proteins contain common targeting sequences, in line with a gradual more specific targeting to the various organelles. See here.