Fig. 1

The most studied chloroplast genome form is circular and very often quadripartite. For each of the three figures, coloured arrows represent nucleotide sequences. \(LSC\) and \(SSC\) stand for long and short single copies (purple and red), respectively. They correspond to regions (subsequences) that are not repeated in the genome. On the opposite, \(IR\) and \(DR\) stand for inverted and direct repeat (green and blue), respectively. a This architecture is the most common one and is defined as a quadripartite architecture. The two green \(IR\) arrows face each other and illustrates that one is the reverse-complement sequence of the other; b the two blue \(DR\) arrows are in the same direction that illustrates both have the same nucleotide sequence; c the two types of repeat can simultaneously exist in the chloroplast genome, and DRs are shorter than IRs