In order to study the effect of an electrical charge of the chromophore, on the efficiency of incorporation of fluorescently-labeled nucleotides into DNA during PCR, three fluorescently-labeled dUPT, one of which with electroneutral and other two with positively and negatively charged dyes (Cy5 analogs), were synthesized. It is shown that dUPT, labeled with electroneutral Cy 5 analog, is most effectively incorporated into DNA when Tag polymerase is used for PCR.