Methods for nucleic acid detection
The present disclosure provides methods and systems for sequencing nucleic acid molecules in a manner that enables higher sequencing accuracy. Methods and systems provided herein may enable sequences that may have low-accuracy reads, such as homopolymer sequences or other repeating sequences, to be determined at a higher accuracy and efficiency.
1. A method for identifying a sequence of a nucleic acid sample, comprising:
(a) providing the nucleic acid sample comprising a first region and a second region, wherein the first region comprises a first homopolymer sequence, wherein the first homopolymer sequence has a first length, wherein the second region does not comprise the first homopolymer sequence;
(b) hybridizing a probe comprising a second homopolymer sequence having a second length to the first homopolymer sequence of the first region, wherein:
(i) a sequence of the first homopolymer sequence is complementary to a sequence of the second homopolymer sequence, and
(ii) the probe yields an observable signal when the second homopolymer sequence is hybridized to the first homopolymer sequence;
(c) detecting the observable signal;
(d) processing an intensity or relative intensity of the observable signal to determine a match between the first homopolymer sequence and the second homopolymer sequence;
(e) using the match determined in (d) to identify the first homopolymer sequence; and
(f) using a sequence-by-synthesis reaction to determine a sequence of the second region.
2. The method of claim 1 , wherein the first length of the first homopolymer sequence is shorter or longer than the second length of the second homopolymer sequence.
3. The method of claim 1 , wherein the second length of the second homopolymer sequence is greater than 5 nucleotides.
4. The method of claim 1 , wherein the observable signal is an optical signal, an electronic signal, or an electromagnetic signal.
5. The method of claim 4 , wherein the optical signal comprises a fluorescent signal.
6. The method of claim 1 , wherein the detecting of (c) comprises imaging.
7. The method of claim 1 , further comprising generating a clonal copy of a target nucleic acid molecule wherein the nucleic acid sample is the clonal copy of the target nucleic acid molecule.
8. The method of claim 1 , wherein the nucleic acid sample is attached to a bead or planar surface.
9. The method of claim 1 , wherein the probe comprises at least one fluorescent label.
10. The method of claim 1 , wherein the probe comprises a sequence of poly(dA), poly(dT), poly(dG), poly(dC), poly(rA), poly(U), poly(rG), or poly(rC).
11. The method of claim 1 , wherein the probe further comprises a random sequence region comprising at least 1 nucleotide in length located at a 5′ or 3′ end of the probe.
12. The method of claim 1 , wherein the probe comprises at least one modified locked nucleotide.
13. The method of claim 1 , wherein the hybridizing of (b) is performed at a first temperature and the detecting of (c) is performed at a second temperature, wherein the first temperature is lower than the second temperature.
14. The method of claim 1 , wherein the detecting of (c) is performed in a presence of a nucleic acid hybridization denaturant.
15. The method of claim 1 , further comprising determining a sequence of the first region.
16. The method of claim 15 , wherein the determining the sequence of the first region comprises synthesizing a complementary strand of the nucleic acid sample using the sequence-by-synthesis reaction, wherein the method further comprises removing a synthesized complementary strand of the nucleic acid sample.
17. The method of claim 1 , wherein the probe further comprises a first bracketing probe and a second bracketing probe, wherein the first bracketing probe hybridizes to a first segment of the first homopolymer sequence and the second bracketing probe hybridizes to a second segment of the first homopolymer sequence.
18. The method of claim 17 , further comprising ligating the first bracketing probe and the second bracketing probe.
19. The method of claim 17 , wherein the first bracketing probe comprises a fluorescence resonance energy transfer (FRET) donor and the second bracketing probe comprises a FRET acceptor, thereby generating a FRET signal, wherein the first homopolymer sequence is identified at least partially based on a strength of the FRET signal.
20. The method of claim 1 , further comprising repeating (b) and (c) at least once with at least one additional probe comprising an additional homopolymer sequence having a length different than the second length, to yield at least one additional observable signal from the at least one additional probe.