Digital amplification
DCFirst Claim
1. A method for detecting quantity of a genetic sequence in a mixed population of human genomic nucleic acid sequences comprising at least a first and a second human genomic sequence, wherein the first sequence is a sequence of a wild-type allele of a locus and a second sequence is a sequence of a mutant allele of the locus, comprising:
- distributing or diluting a mixed population of cell-free, human genomic nucleic acid template molecules from a sample in which the fraction of mutant alleles is less than 20%, into a set comprising at least fifteen assay samples such that said at least fifteen assay samples each comprises less than ten template molecules;
amplifying the template molecules in the assay samples, wherein an assay sample with a single template molecule forms homogeneous amplification products in the assay sample;
analyzing by determining nucleic acid sequence of amplification products in the assay samples of the set with homogeneous amplification products to determine a first number of assay samples in the set which contain the first sequence and a second number of assay samples in the set which contain the second sequence;
comparing the first number to the second number to ascertain a ratio which reflects the composition of the mixed population;
identifying a mutation in the mixed population if a statistically significant fraction of assay samples comprises the second sequence.
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Litigations
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Accused Products
Abstract
The identification of pre-defined mutations expected to be present in a minor fraction of a cell population is important for a variety of basic research and clinical applications. The exponential, analog nature of the polymerase chain reaction is transformed into a linear, digital signal suitable for this purpose. Single molecules can be isolated by dilution and individually amplified; each product is then separately analyzed for the presence of pre-defined mutations. The process provides a reliable and quantitative measure of the proportion of variant sequences within a DNA sample.
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Citations
28 Claims
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1. A method for detecting quantity of a genetic sequence in a mixed population of human genomic nucleic acid sequences comprising at least a first and a second human genomic sequence, wherein the first sequence is a sequence of a wild-type allele of a locus and a second sequence is a sequence of a mutant allele of the locus, comprising:
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distributing or diluting a mixed population of cell-free, human genomic nucleic acid template molecules from a sample in which the fraction of mutant alleles is less than 20%, into a set comprising at least fifteen assay samples such that said at least fifteen assay samples each comprises less than ten template molecules; amplifying the template molecules in the assay samples, wherein an assay sample with a single template molecule forms homogeneous amplification products in the assay sample; analyzing by determining nucleic acid sequence of amplification products in the assay samples of the set with homogeneous amplification products to determine a first number of assay samples in the set which contain the first sequence and a second number of assay samples in the set which contain the second sequence; comparing the first number to the second number to ascertain a ratio which reflects the composition of the mixed population; identifying a mutation in the mixed population if a statistically significant fraction of assay samples comprises the second sequence. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for detecting quantity of a genetic sequence in a mixed population of human genomic nucleic acid sequences comprising at least a first and a second human genomic sequence, wherein the first sequence is a sequence of a wild-type allele of a locus and a second sequence is a sequence of a mutant allele of the locus, comprising:
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distributing or diluting a mixed population of cell-free, human genomic nucleic acid template molecules into a set comprising at least fifteen assay samples such that said at least fifteen assay samples comprise an average of 0.5 molecules of template per assay sample; amplifying the template molecules in the assay samples, wherein an assay sample with a single template molecule forms homogeneous amplification products in the assay sample; analyzing by determining nucleic acid sequence of amplification products in the assay samples of the set with homogeneous amplification products to determine a first number of assay samples in the set which contain the first sequence and a second number of assay samples in the set which contain the second sequence; comparing the first number to the second number to ascertain a ratio which reflects the composition of the mixed population; identifying a mutation in the mixed population when a statistically significant fraction of assay samples comprises the second sequence. - View Dependent Claims (26, 27, 28)
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Specification