Segmented Nucleic Acid Primers for Rare Allele Detection
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Solution Overview
Problem
Current nucleic acid amplification methods struggle to selectively amplify rare nucleic acids in the presence of overwhelming excess of non-target nucleic acids, often leading to false-positive results due to the amplification of pseudo-target alleles that differ from the target by only a single nucleotide.
Innovation Solution
The development of engineered nucleic acids, such as single-stranded primers (ssPrimers) and partially double-stranded blockers (dsBlockers), which selectively bind to rare target alleles and suppress the amplification of abundant wild-type alleles by utilizing specific binding domains and mechanisms like strand displacement and thermodynamic specificity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nucleic acid amplification methods are used, then amplification efficiency is high, but selectivity deteriorates leading to false-positive results from pseudo-target alleles
Solution Approach 1:
The primer is divided into functionally distinct domains: a specificity domain (SD) that binds to the target allele and a priming domain (PD) that initiates amplification. This segmentation allows the SD to provide high selectivity by recognizing specific allelic sequences while the PD maintains amplification efficiency, resolving the contradiction between detection accuracy and amplification productivity
Solution Approach 2:
Different regions of the primer are assigned different functional properties: the SD region is optimized for high-specificity binding to the target allele through complementary base pairing, while the PD region is optimized for efficient primer extension by polymerase. This local differentiation enables the primer to simultaneously achieve high selectivity at the binding site and high amplification efficiency at the extension site
2Measurement precision
If amplification conditions are optimized for high selectivity, then false-positives are reduced, but amplification efficiency decreases
Solution Approach 1:
The specificity domain acts as an intermediary element that mediates between the primer and target allele. It provides a recognition interface that discriminates target from pseudo-target alleles through sequence-specific binding, while the priming domain serves as the functional intermediary that executes amplification. This dual-domain architecture allows optimization of each domain's function independently, maintaining both precision and productivity
3Quantity of substance
If standard primers are used that bind to both target and pseudo-target alleles, then amplification efficiency is maintained, but measurement precision deteriorates due to inability to distinguish rare alleles
Solution Approach 1:
The specificity domain performs preliminary recognition and selection of the target allele before amplification begins. By pre-binding to the specific sequence of the rare allele through complementary base pairing, the primer ensures that only the intended target is amplified, preventing co-amplification of pseudo-target alleles and enabling detection of rare alleles even at very low abundances
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
These engineered nucleic acids enhance the selective amplification of rare target alleles while minimizing the amplification of pseudo-target alleles, thereby reducing false-positive results and improving the accuracy of nucleic acid detection assays.
Implementation Method 1
nucleic acids (e.g., oligonucleotides, such as oligonucleotides less than 100 nucleotides in length) engineered to contain specific binding domains that enhance the amplification of a (e.g., at least one) target nucleic acid
Implementation Method 2
extending the priming domain at its 3' end in a target-complementary manner in the presence of a polymerase
Data Source
AI summary
The present disclosure provides, in various aspects and embodiments, methods and compositions for selectively amplifying a rare target nucleic acid and/or suppressing amplification of non-target nucleic acids with sequences similar to the rare target nucleic acid. The methods and composition are useful, for example, for detecting rare alleles among a population of wild-type alleles.