NEW MATERIAL:The compound of formula I [R1 and R2 are H, phosphoric acid residue or group of formula II (a and b are arbitrary natural numbers and b+1≥a; R3 is bivalent hydrocarbon residue; X is O or imino; Y is labeling substance linked to Lys by covalent bond)' n is arbitrary natural number; B is base constituting nucleotide].

USE: A reagent for cloning a gene or a reagent for diagnosis of genetic diseases.

PREPARATION: The compound of formula I for probe can be produced e.g. by aminoalkylating a nucleotide compound of 15W40 nucleoside units such as fragment of gene, introducing polylysine into the obtained compound and reacting and linking a labeling substance such as fluorescein isothiocyanate to the polylysine.