Blocking Oligonucleotide Mismatch for DNA Amplification Specificity
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Solution Overview
Problem
Current methods for detecting variant DNA sequences, especially those with nucleotide substitutions, lack specificity and are inefficient in distinguishing between target and reference sequences, particularly when the variants are present in low quantities.
Innovation Solution
An in vitro PCR method using a blocking oligonucleotide with a sequence mismatch outside the target mutation site is employed, allowing for selective amplification of target DNA sequences by competing with generic primers and enhancing discrimination between variant and wild-type sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a blocking oligonucleotide without mismatch is used, then wild-type sequence amplification is effectively blocked, but specificity for detecting nucleotide substitution variants is insufficient
Solution Approach 1:
The blocking oligonucleotide is designed with non-complementary nucleotides at specific positions (outside the target mutation site) to create local differences in binding affinity. This allows the oligonucleotide to maintain strong binding to wild-type sequences while having reduced binding to variant sequences with specific nucleotide substitutions, thereby achieving both effective blocking and high specificity simultaneously
Solution Approach 2:
The invention modifies the blocking oligonucleotide sequence by introducing non-complementary nucleotides at specific positions, changing its binding parameters. This sequence modification creates differential binding characteristics that enable selective blocking of wild-type amplification while preserving the ability to detect specific variant sequences with nucleotide substitutions
2Ease of operation
If conventional PCR methods are used, then the process is simple and time-efficient, but sensitivity for detecting low-frequency mutant alleles is limited
Solution Approach 1:
The blocking oligonucleotide acts as an intermediary element that selectively interferes with wild-type sequence amplification. By introducing this intermediary component to the conventional PCR system, the method achieves sensitive detection of low-frequency mutant alleles while maintaining the relative simplicity of PCR-based approaches
Solution Approach 2:
The blocking oligonucleotide is designed to preemptively bind to wild-type sequences before amplification can occur, preventing their amplification. This preliminary blocking action enriches the relative proportion of mutant alleles in the amplification mixture, enabling detection of low-frequency variants that would otherwise be masked by the excess of wild-type sequences
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method significantly improves the specificity of detecting target sequences, enabling the detection of low-frequency mutations with high accuracy, as demonstrated by improved Ct values and sensitivity in mutant samples compared to methods without mismatches.
Implementation Method 1
a blocking oligonucleotide complementary to a portion of the reference DNA sequence comprising the target mutation site
Implementation Method 2
The blocking primer encompasses the target mutation site and is complementary to the wild-type sequence. One of the two generic primers overlaps with the blocking primer by several bases, neighboring the target mutation site, and thus is in competition with the blocking primer.
Data Source
AI summary
The invention relates to an in vitro method for selectively amplifying a target DNA sequence from a nucleic acid sample, which method comprises running a PCR amplification of a nucleic acid sample suspected of comprising at least one target DNA sequence that differs from a reference DNA sequence at at least one predetermined target mutation site; wherein said method employs a blocking oligonucleotide complementary to a portion of the reference DNA sequence comprising the target mutation site, with the exception of a least one mismatch outside the target mutation site.