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Method of determining the presence and quantifying the number of di- and trinucleotide repeats

  • US 5,650,277 A
  • Filed: 10/04/1994
  • Issued: 07/22/1997
  • Est. Priority Date: 07/02/1992
  • Status: Expired due to Fees
First Claim
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1. A method of quantifying the number of trinucleotide repeats in a nucleic acid of interest, comprising the steps of:

  • (a) if the nucleic acid of interest is double stranded, treating the nucleic acid of interest to obtain unpaired nucleotide bases spanning the trinucleotide repeats and their flanking regions, or, if the nucleic acid of interest is single stranded, directly employing step (b);

    (b) contacting the unpaired nucleotide bases spanning the number of trinucleotide repeats and their flanking regions with an oligonucleotide primer for hybridizing with a stretch of nucleotide bases present in the nucleic acid of interest partially or fully 3'"'"' of the nucleotide repeats to be quantified, so as to form a duplex between the primer and the nucleic acid of interest;

    (c) providing means for confining the nucleic acid of interest and the oligonucleotide primer to a reaction chamber at all further steps (d) through (k); and

    further comprising the cycled steps of;

    (d) contacting the template primer duplex with a first primer extension unit for base pairing with one of the nucleotide bases, in the core sequence of the trinucleotide repeats, and with a template dependent extension enzyme;

    (e) eliminating non-incorporated units of said first primer extension units;

    (f) contacting the template primer duplex, which primer is now extended by one unit as described in step (d), with a second primer extension unit for base pairing with a second nucleotide base, in the core sequence of the repeat, said second nucleotide base being located adjacent to and immediately 5'"'"' of the nucleotide base employed under step (d), and with a template dependent extension enzyme;

    (g) eliminating non-incorporated units of said second primer extension units;

    (h) contacting the template primer duplex, which primer is now elongated by one further additional unit as described in step (f), with;

    (i) a third primer extension unit for base pairing with a third nucleotide base, in the core sequence of the repeat, said third nucleotide base being located adjacent to and immediately 5'"'"' of the nucleotide base under step (f);

    (ii) a detection moiety which is conjugated with a fourth primer extension unit for base pairing with a nucleotide base 5'"'"' of the repeats, said nucleotide base being the first nucleotide base of a type not included among the nucleotide bases in the core sequence of the trinucleotide repeats, said detection moiety which is conjugated with said fourth primer extension unit may be present in selected cycles of this stage; and

    (iii) a template dependent extension enzyme;

    (i) eliminating non-incorporated units of said third and fourth primer extension units;

    (j) if step (h) included said detection moiety which is conjugated with said fourth primer extension unit, detecting the presence of said detection moiety; and

    if no detection is obtained,(k) repeating steps (d) to (j) until said detection moiety is detected, said detection of said detection moiety being indicative of the number of trinucleotide repeats included in the nucleic acid of interest.

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