Methods of amplifying and sequencing nucleic acids
An apparatus and method for performing rapid DNA sequencing, such as genomic sequencing, is provided herein. The method includes the steps of preparing a sample DNA for genomic sequencing, amplifying the prepared DNA in a representative manner, and performing multiple sequencing reaction on the amplified DNA with only one primer hybridization step.
1. A method of sequencing a target nucleic acid, comprising:
a) converting a reference nucleic acid sequence into a reference number sequence comprising a plurality of reference numbers each representing an ideal signal from a nucleotide triphosphate, wherein the reference number sequence further comprises an organization that represents an order of sequential introduction of a plurality of the nucleotide triphosphates;
b) detecting signals when a plurality of the nucleotide triphosphates are introduced in the sequential order over one or more copies of a fragment of the target nucleic acid, each signal corresponding to a query number of a query number sequence indicative of a nucleic acid sequence of said fragment, wherein the query number sequence comprises the order that represents the sequential introduction of the plurality of the nucleotide triphosphates;
c) matching the query number sequence to a contiguous subset of the reference number sequence at one or more positions;
d) comparing the similarity of the query number sequence to the reference number sequence to generate a quality score, wherein the quality score is indicative of the quality of the match between the query number sequence and the contiguous subset of the reference number sequence;
e) repeating steps b) through d) for a plurality of different fragments of the target nucleic acid;
f) anchoring the query number sequences from a plurality of the fragments at the positions on the reference number sequence corresponding to the match with the highest quality score;
g) averaging the query numbers of one or more of the query number sequences at each sequence position of the reference number sequence that is covered by the one or more query number sequences, thereby generating a consensus number sequence; and
h) converting the consensus number sequence into a nucleic acid sequence.
2. The method of claim 1 , further comprising dividing the reference number sequence into overlapping, ideal sub reference number sequences of a predetermined length, and indexing the ideal sub reference number sequences.
3. The method of claim 2 , further comprising dividing each query number sequence into a plurality of query sub number sequences, each having a length corresponding to the predetermined length of the ideal sub reference number sequences.
4. The method of claim 3 , further comprising searching the indexed ideal sub reference number sequences to determine a position for matching the query sub number sequences to the reference number sequence.
5. A method of sequencing a target nucleic acid, comprising:
a) detecting signals when a plurality of nucleotide triphosphates are introduced in a sequential order over one or more copies of a fragment of the target nucleic acid;
b) associating each signal to a query number of a query number sequence indicative of the nucleic acid sequence of the fragment;
c) repeating steps a) and b) to produce a plurality of the query number sequences for a plurality of different fragments;
d) comparing the plurality of query number sequences to one another to identify a plurality of overlapping regions between the plurality of query number sequences;
e) matching the plurality of the query number sequences at the overlapping regions;
f) generating a quality score based on the matching, wherein the quality score is indicative of the quality of the match;
g) identifying a plurality of pair-wise overlapping query number sequences by determining matches having a quality score meeting a predetermined threshold;
h) grouping the pair-wise overlapping query number sequences into one or more unitigs;
i) averaging the sequence numbers of the query number sequences at each of one or more matching positions within each unitig, thereby generating a consensus number sequence which comprises a unitig consensus number sequence; and
j) converting each unitig consensus number sequence into a unitig consensus nucleic acid sequence.
6. The method of claim 5 , wherein the one or more unitigs in step h) comprise consistent chains of maximal overlap of the query number sequences.
7. The method of claim 5 , further comprising the steps of:
k) comparing unitig consensus nucleic acid sequences to each other to identify sequence overlaps; and
l) joining unitig consensus having common overlapping sequences, thereby forming one or more contigs comprising contig nucleic acid sequences.
8. The method of claim 7 , further comprising the steps of:
m) identifying boundaries within each contig, wherein a boundary is a region where unitig sequences diverge from a common region; and
n) breaking contigs at boundaries identified in step m).
9. The method of claim 8 , further comprising the step of:
o) joining any two contigs whose ends are overlapped by the same fragment nucleic acid sequence, wherein optionally the contigs thus joined are broken if a boundary is identified.
10. The method of claim 9 , further comprising the steps of:
p) identifying all matches between fragment nucleic acid sequences and the contigs; wherein optionally the contigs are broken at any position where fewer than 4 fragment nucleic acid sequences are matched;
q) calculating contig consensus number sequences by averaging the sequence numbers of the query number sequences associated with the fragment nucleic acid sequences aligned to contigs in step p); and
r) converting the contig consensus number sequences into contig consensus nucleic acid sequences.
11. The method of claim 10 , further comprising repeating steps p) through r) with the contig consensus nucleic acid sequences until substantially no consensus base calls change, thereby calculating a final contig consensus sequence.