The DNA of cyanelles which are described as endosymbiotic cyanobacteria from Cyanophora paradoxa (strain LB555UTEX) is equivalent to 127 kilobasepairs. It is characterized by two inverted repeat segments, 10 kilobasepairs in size, which are separated from each other by long single-copy DNA segments of unequal size. This morphology of the chromosome is also found in the chloroplast DNA of most higher plants and some green algae. The cyanelle DNA exists in two forms of circular molecules which differ only in the orientation of the two single-copy DNA segments relative to each other. This is likely due to intramolecular recombination within the inverted repeat segments.
