or self-cloning consisting in the removal of nucleic acid sequences from a cell of an organism followed by reinsertion of all or part of that nucleic acid sequence. Therefore, the use of endogenous dominant selection markers, such as: genes for mutated acetohydroxyacid synthase (ahas) [21] or mutated pds ([37], this paper) for transformation of microalgae is an important prerequisite for the creation of safe and applicable transgenic microalgae. We have demonstrated here that the cassette containing the selection marker and the associated transgene can be easily excised from the plasmid and used successfully for transformation and insertion of additional transgenes both 3′ and 5′ of the selection marker, to create self-cloned strains without foreign DNA inserted.