Methods and processes for calling bases in sequence by incorporation methods
Computer implemented methods, and systems performing such methods for processing signal data from analytical operations and systems, and particularly in processing signal data from sequence-by-incorporation processes to identify nucleotide sequences of template nucleic acids and larger nucleic acid molecules, e.g., genomes or fragments thereof.
1. A system for identifying a nucleotide in a nucleic acid sequence, comprising:
an array comprising a plurality of reaction locations, wherein each reaction location contains a respective sequencing reaction, in a plurality of sequencing reactions, wherein each reaction location contains a respective sequencing reaction, in a plurality of sequencing reactions that produces optical signals during a template dependent primer extension reaction comprising a set of differentially labeled nucleotide analogs, the analogs comprising different labels in a plurality of different labels, wherein each respective different label in the plurality of different labels is associated with a unique reference spectral signature in a plurality of reference spectral signatures;
an excitation light source providing illumination to the plurality of reaction locations;
a first detector configured for receiving an optical signal from the sequencing reaction, wherein a first reference spectral signature in the plurality of reference spectral signatures is uniquely associated with a first portion of the first detector and a second reference spectral signature in the plurality of reference spectral signatures is uniquely associated with a second portion of the first detector, wherein the first portion is other than the second portion;
a data processing unit comprising software for:
a) identifying the optical signal as an incorporation signal associated with incorporation of a base from one of the differentially labeled nucleotide analogs into a nascent strand, wherein the base is unlabeled following the incorporation;
b) classifying the incorporation signal as corresponding to one of the labels on one of a differentially labeled nucleotide analog based upon a plurality of pulse metrics for the incorporation signal, wherein the plurality of pulse metrics includes both an intensity and a measured spectral signature, and wherein the classifying comprises matching the measured spectral signature to a reference spectral signature in the plurality of reference spectral signatures thereby providing a pulse classification of the incorporation signal that is correlated to a particular one of the differentially labeled nucleotide analogs; and
c) calling the base in the nucleic acid sequence using the pulse classification and at least one additional signal characteristic after the pulse classification has been provided for the incorporation signal.
2. The system of claim 1 , wherein the matching comprises determining a probability that said reference spectral signature fits with the measured spectral signature of the incorporation signal.
3. The system of claim 1 , wherein the identifying further distinguishes the optical signal from background or noise signals.
4. The system of claim 1 , wherein the plurality of pulse metrics further comprises at least one of signal to noise ratio, pulse width, pulse shape, time interval to end of preceding pulse, and time interval to ensuing pulse.
5. The system of claim 1 , wherein the receiving, identifying, classifying, and calling are performed in real time during the template dependent primer extension reaction.
6. The system of claim 1 , wherein the reaction locations are within optical confinements.
7. The system of claim 6 , wherein the optical confinements are zero mode waveguides.
8. The system of claim 1 , wherein the excitation light source comprises at least one laser.
9. The system of claim 1 , wherein the optical signal is passed through optical components prior to reaching the first detector.
10. The system of claim 1 , wherein the sequencing reaction comprises a polymerase/template/primer complex.
11. The system of claim 1 , further comprising a database for storing the plurality of pulse metrics in a non-transitory computer-readable format, wherein the pulse metrics include both the intensity and the measured spectral signature.
12. The system of claim 1 , wherein the measured spectral signature comprises measurement values from a plurality of pixels from a portion of the first detector.
13. The system of claim 12 , wherein the measurement values from the plurality of pixels from the portion of the first detector are collapsed or combined prior to extracting them from the first detector.
14. The system of claim 1 , wherein the at least one additional signal characteristic is a background signal level for the optical signal.
15. The system of claim 1 , wherein the at least one additional signal characteristic is an intensity or duration of a signal received adjacent to the optical signal.
16. The system of claim 1 , wherein the plurality of reaction locations are regularly spaced.
17. The system of claim 1 , further comprising a display on which to present the output of at least one of the identifying, classifying, and calling performed by the data processing unit.
18. The system of claim 1 , wherein the differentially labeled nucleotide analogs are each labeled at a terminal phosphate group.
19. The system of claim 1 , wherein the plurality of reaction locations comprise optically resolvable single molecule complexes.
20. The system of claim 1 , comprising an array of detectors configured for receiving optical signals from a plurality of sequencing reactions, wherein each of the sequencing reactions provides optical signals to only one of the detectors in the array of detectors, and wherein the array of detectors includes the first detector.
21. The system of claim 1 , comprising an array of detectors, wherein the array of detectors and the reaction locations are manufactured to have a fixed association, and wherein the array of detectors includes the first detector.