Abstract
Morphology and organization of tobacco plastid genome was analyzed by pulse-field gel electrophoresis and observation of individual plastid genomes through a fluorescence microscope. Each single molecule of plastid genome was detected as either a circular or a linear DNA molecule in four forms; monomer, dimmer, trimer and tetramer. Pattern of restriction enzyme fragment showed the presence of linear molecule that has defined ends in internal sequence of inverted repeats. Linear molecule having specific ends were found in plastid DNA isolated from shoots that contain young leaves and meristematic tissues although it were not found in plastid DNA of mature leaves. It seems that linear plastid genome having specific ends are not results of a breakage of circle genome during extraction, but it may have a relation with DNA replication in plastids.
