Minicircle DNA consists only of the specific GOI and a very short sequence which inevitably remains in the minicircle as the remnant of the specific production process. In comparison to typical plasmid DNA with the general portion known as the «backbone», comprising the genetic marker for selection (e.g. by antibiotics) and the so-called origin of replication (ori; for the replication of the plasmids in E. coli cells), minicircles are extremely small – down to half the size of the smallest plasmids. Since the backbone sequences comprise typical motifs of prokaryotic DNA and may also be methylated differently (CpG motifs), they hamper transfection of eukaryotic cells. As quality controls show, chromatographic purification carried out during minicircle production by PlasmidFactory results in the highest purity of minicircle DNA, in the quality range of ccc Grade DNA. For reproducibility of experimental data it is mandatory to use high purity DNA, since even trace amounts of contaminants may lead to significant artefacts in the experiment.