Primer extension methods for detecting nucleic acids

Abstract

Methods are provided for selective nucleic acid sequence detection in single base primer extension reactions of high sensitivity. These methods are useful for detecting small amounts of mutant nucleic acid in a heterogeneous biological sample. These methods are particularly useful for identifying individuals with gene mutations indicative of early colorectal cancer.

What is claimed is:  
     
         1 . A method for identifying a single nucleotide in a nucleic acid sample, the method comprising the steps of: 
 (a) annealing an oligonucleotide primer to a nucleic acid sample under conditions that promote exact complementary hybridization between said primer and a portion of a nucleic acid in said sample;    (b) extending said primer by a single base;    (c) separating said extended primer from said portion;    (d) repeating steps (a) through (c); and    (e) identifying the base incorporated into said extended primer, thereby to identify said single nucleotide.    
     
     
         2 . The method of  claim 1 , wherein said base in step (b) is a chain-terminating nucleotide.  
     
     
         3 . The method of  claim 1 , wherein said extension reaction in step (b) is performed by addition of one or more chain-terminating nucleotides.