Multi-pass sequencing
Improved single molecule sequencing methods, compositions, and devices, are provided. In a first aspect, the present invention provides a multi-pass method of sequencing a target sequence using nanopore sequencing, the method comprising: i) providing a non-naturally occurring concatemer nucleic acid molecule comprising a plurality of copies of the target sequence; ii) nanopore sequencing at least three copies of the target sequence in the concatemer, thereby obtaining a multi-pass sequence dataset, wherein the multi-pass sequence dataset comprises target sequence datasets for the at least three copies of the target sequence; and iii) using the multi-pass sequence dataset to determine the target sequence.
1. A multi-pass method of sequencing a target sequence using nanopore sequencing, the method comprising:
i) providing a non-naturally occurring concatemer nucleic acid molecule comprising monomeric units that comprise (a) the target sequence, and (b) a non-target sync sequence having a predetermined sequence,
wherein copies of the target sequence are separated by non-target sync sequences that demarcate a target sequence boundary,
wherein the concatemer comprises a plurality of copies of the target sequence and a plurality of copies of the sync sequence; and then
ii) nanopore sequencing at least three copies of the target sequence in the concatemer, thereby obtaining a multi-pass sequence dataset, wherein the multi-pass sequence dataset comprises target sequence datasets for the at least three copies of the target sequence; and
iii) using the multi-pass sequence dataset to determine the target sequence wherein the non-target sync sequences are used to align the target sequences in the multi-pass sequence dataset.
2. The method of claim 1 , wherein the nanopore sequencing further comprises sequencing at least four sync sequences.
3. The method of claim 2 , wherein all of the sync sequences are the same.
4. The method of claim 2 , wherein the sync sequences are shorter than the target sequence.
5. The method of claim 1 , wherein the multi-pass sequence has an accuracy of at least Q6.
6. The method of claim 1 , wherein the concatemer comprises at least 5 copies, optionally at least 8 copies, of the target sequence.
7. The method of claim 1 , wherein the concatemer comprises a calibration sequence.
8. The method of claim 1 , wherein the providing the concatemer comprises circularizing a nucleic acid fragment comprising the target sequence to produce a circular nucleic acid; and using the circular nucleic acid as a template for rolling circle replication, thereby providing a concatemer.
9. The method of claim 7 , wherein the nanopore sequencing in step (ii) comprises sequencing the calibration sequence, thereby obtaining calibration information, and further comprises using the calibration information to model base-calling for one or more nanopore channels.
10. The method of claim 9 , wherein the concatemer contains one copy of the calibration sequence.
11. The method of claim 9 , wherein the concatemer contains two copies of the calibration sequence.
12. The method of claim 9 wherein the concatemer comprises two different calibration sequences.
13. The method of claim 9 wherein the concatemer comprises no more than 3 copies of the calibration sequence.
14. The method of claim 9 wherein the calibration sequence(s) is not within a monomeric unit.
15. The method of claim 9 , wherein step iii) comprises using the calibration information to optimize the base call model to the particular electrical and physical properties of the nanopore from which the calibration information is derived.
16. The method of claim 9 wherein the target sequence is genomic DNA or is complementary DNA transcribed from mRNA or rRNA.
17. The method of claim 9 , wherein the concatemer nucleic acid molecule comprises 3-300 monomers and comprises a calibration sequence outside of the 3-300 monomers or comprises a pair of calibration sequences that flank the 3-300 monomers.