Are of appropriate size to be descendants of eubacteria. Have inner membranes containing several enzymes and transport systems similar to those on prokaryotic plasma membranes. Replicate by splitting processes similar to binary fission present in prokaryotes. Have DNA which is circular and not associated with histones or other proteins, as in prokaryotes. Contain their own tRNA, ribosomes, and other components for DNA transcription and translation into proteins.
Mitochondrial ribosomes vary, but are also more similar to prokaryotic ribosomes.
Molecular systematics lends even more evidence to support the endosymbiotic theory. The rRNA of chloroplasts is more similar in base sequence to RNA from certain photosynthetic eubacteria than to rRNA in eukaryotic cytoplasm. Mitochondrial rRNA also has a base sequence which supports a eubacterial origin. The origins of mitosis and meiosis which also utilize microtubules. Mitosis made it possible for large eukaryotic genomes to be reproduced.