Abstract: A fragment, synthetic or natural, DNA or RNA, may be attached to a non-radiological label such as a fluorescent compound, a luminescent compound or a color reflective compound, by a linker. The linker is an aminoalkylphosphoramide. The linker may contain a number of methyl units selected to adjust the mobility of the arrangement of the tagged fragment in a polyacrylamide gel during electro-phoresis. A unique color may be attached to each for the four bases. The color coded bases may be separated in a single lane of the ployacrylamide gel. Because the mobility of each arrangement has been adjusted the normal one base spacing will be produced. The sequence of the target may be read directly by manually observing the color sequence or by an automatic reader. The tagging of natural fragments may be used to tag a preselected gene, in the application of Southern and Northern bloting diagnostic procedures, as a diagnostic tool to hunt/detect selected DNA and to label probes to detect ribosonal RNA of pathogens.