If very little template is used, a corresponding increase in the number of amplification cycles will be needed to obtain a sufficient amount of product. A Taq polymerase that is used for most PCR experiments does not feature a correction function (3'-5' exonuclease activity); thus, errors occurring during amplification cannot be corrected. The higher the number of cycles, the more prevalent the amplification of flawed product will be. If, on the other hand, the amount of template is too high, the probability of primers annealing to other (not one hundred percent complimentary) sequences, as well as the formation of primer dimers, will increase, which will result in the amplification of by-products. In many cases, DNA is isolated from cell cultures or from microorganisms and subsequently used as a PCR template. Following purification, it is necessary to determine the concentration of the DNA to be able to define the volume that is required for the PCR setup. While agarose gel electrophoresis may serve to provide an estimate, this method is far from accurate. UV-Vis spectrophotometry has been established as the gold standard for the quantification of nucleic acids; this direct and therefore easy and quick method measures absorbance of the sample at 260 nm, and concentration is calculated with the help of a conversion factor.