Patent ID: 8354225

Claim:
A process for increasing the number of copies of a portion of an initial oligonucleotide, wherein said portion incorporates one or more non-standard nucleotide units incorporating the heterocycles selected from the group consisting of 2,-4-diaminoyprimidine and xanthosine, wherein said process comprises: (a) contacting said initial oligonucleotide with an enzyme, nucleoside triphosphates that are complementary to the standard and non-standard nucleotides in the initial oligonucleotide, and a first oligonucleotide primer that is complementary to a part of said initial oligonucleotide, and incubating the contacted mixture under conditions where said enzyme synthesizes an extension product of the first primer that is complementary to said initial oligonucleotide, wherein said first primer is selected so as to be sufficiently complementary to the initial oligonucleotide that it hybridizes therewith, such that the extension product synthesized from the first primer, when it is separated from its complement, can serve as a template for synthesis; (b) separating the extension products from the initial oligonucleotides on which they were synthesized to produce single-stranded molecules; and; (c) adding to the mixture containing the single-stranded extension products generated from steps (a) and (b) a second oligonucleotide primer that is complementary to a part of said extension products, and incubating the mixture containing the first and second primer under conditions where the enzyme synthesizes a complement of the initial oligonucleotides as well as the extension product to generate products that are extension products of both primers, wherein said second primer is selected so as to be sufficiently complementary to the extension product of the initial oligonucleotide so that it hybridizes therewith, such that the extension product synthesized from the second primer, when it is separated from its complement, can serve as a template for synthesis.