| Abstract
| - In parallel with a large-scale sequencing effort, the humangenome project will need next-generation tools for accurate and efficient analyses of the enormous pool of DNAsequences. Such analyses are required for (a) validationof DNA sequences, (b) comparison of a parent (known)sequence with a related (unknown) sequence, and (c)characterization of sequence polymorphisms in variousgenes, especially those associated with genetically inherited human diseases. Here, we report a novel method thatcombines stable isotope 13C/15N labeling of PCR productsof the target sequences with analysis of the mass shiftsby mass spectrometry (MS). The mass shift due to thelabeling of a single type of nucleotide (i.e., A, T, G, or C)reveals the number of that type of nucleotide in a givenDNA fragment. Using this technique, we have accuratelydetermined nucleotide compositions of DNA fragments.The method has also been applied to score a knownsingle-nucleotide polymorphism (SNP). The comparisonsof nucleotide compositions determined by our methodamong homologous sequences are useful in sequencevalidation, sequence comparison, and characterizationsof sequence polymorphisms.
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