A method is provided for determining the identity of at least two discrete single nucleotide bases each adjacent to a predetermined nucleotide base sequence in a target sample comprising one or more types of polynucleotide chain, the method comprising incorporating a capture group into the target sample and immobilising the target sample by means of the capture group; mixing the target sample with (i) nucleotide primers which are complementary to the characterised base sequences such that they anneal thereto at positions adjacent to the bases to be identified and (ii) at least two types of dideoxynucleoside triphosphate (ddNTP), each type labelled with a distinguishable fluorescent group, and (iii) a nucleotide chain extending enzyme such that ddNTPs complementary to the bases to be identified are incorporated into the nucleotide primers; eluting the extending nucleotide primers, separating the types of extended nucleotide primer on basis of size or charge and identifying the ddNTPs incorporated into each type of nucleotide primer by reference to the fluorescent characteristics associated with the distinguishable groups. Primers and a test kit are provided for use in performance of the method.