A great deal of evidence supports the __ origin of mito and plastids. The inner membranes of both have enzymes and transport systems that are homologous to those found in the plasma membranes of living prok. Mitochondria and plastids replciate by a splitting process that is similar to that of certain prok. In addition, each of these organelles contains a single, circular DNA molecule that, like the chromosomes of bacteria, is not associated with __ or large amounts of other proteins. As might be expected of organelles descended from free-living organisms, mito and plastids also have the cellular machinery (including __ ) needed to transcribe and translate their DNA into proteins. Finally, in terms of siez, nucleotide sequence and sensitivity to certain antibiotics, teh ribosomes of mitochondria and plastids are more similar to _- ribosomes than they are to the cytoplasmic ribosomes of __ cells.