A kit for the isolation of a target polynucleotide from a sample, comprising:an oligodeoxyribonucleotide comprising a defined sequence of nucleoside subunits joined by inter-subunit linkages and defined by the formula: ##STR2## wherein B is a purine or pyrimidine or an analog thereof and n is between 2 and 48 and wherein said oligodeoxyribonucleotide hybridizes to said target polynucleotide. 33.