| 摘要 |
A composite nucleic acid primer for a reaction of an enzymatic extension of primer on a template strand; which composite primer comprises two or more covalently unconnected oligonucleotides. Each of the oligonucleotides comprises a binding segment complementary to a binding site in the template strand. The binding segment and the binding site are selected to bind the oligonucleotide to the template strand by means of annealing between the binding segment and the binding site. The binding sites for different oligonucleotides are selected close enough in the template strand to enhance the sequence specificity of priming by the composite primer, as compared to the sequence specificity of priming by one of the oligonucleotides alone. Each of the two oligonucleotides has a segment, preferably 5 to 6 bases long, binding to the template strand. The total primer-to-template annealing length being 10 to 12 bases, the priming site is sufficiently unique in a plasmid size template. An oligonucleotide library (collection) containing an appreciable portion of all possible sequences of a 5-mer segment can be as small as a few hundred samples. The composite primer libraries have fewer samples than a library of similarly unique non-composite primers by about two orders of magnitude, being thus more affordable to users.
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