Nucleotide polymorphism detection method

Abstract

A method for characterising a DNA analyte comprised of one or more polynucleotide types characteristic of a site of nucleotide polymorphism each of which includes a target region having the formula -X-Y-Z- wherein X and Z are respectively first and second characteristic flanking oligonucleotide regions and Y is one of the variants constituting the site is provided. The method is characterised by the steps of; (a) reacting a single-stranded oligonucleotide including the target region derived from at least one of the polynucleotide types with a set of unused probes comprised of (i) a single-stranded first aptamer terminating at its 3' end in a sequence complementary to that of -X or -X-Y and (ii) one or more second single-stranded aptamers terminating at their 5′ end in a sequence complementary to that of -Z-Y or -Z (as the case may be) and labelled with detectable elements which are in an undetectable state in the presence of a ligase to create a substantially double-stranded used probe comprised of the oligonucleotide, first aptamer and one of the second aptamers; (b) wholly or in part digesting the used probe with an exonuclease or polymerase exhibiting exonuclease activity in a 3′ to 5′ direction into its constituent single nucleotides at least one of which includes a detectable element now in a detectable state and (c) thereafter detecting the detection property associated with the now detectable element thereby identifying the nature of the Y variant and therefore the allele it gives rise to. A second mirror-image method is also disclosed. Also provided are vesicles in which the method can be carried out. The method is suitable for a range of diagnostic screening applications including the detection of mutant alleles associated with genetic disorders and cancer.