Several lines of evidence support the endosymbiotic theory. First, mitochondria and chloroplasts contain their own DNA, which is distinct from the nuclear DNA of the cell and is similar to bacterial DNA in both structure and sequence. Second, these organelles replicate independently of the cell through a process similar to bacterial binary fission. Third, both mitochondria and chloroplasts have double membranes, consistent with the engulfing mechanism proposed by the theory. Lastly, the ribosomes within these organelles resemble bacterial ribosomes in size and sensitivity to antibiotics.
