Visible Genetics Inc.

Rodney D Gilchrist

Vrijmoed Chi

John K Stevens

Gregory Dee

Ronald J Green

James M Dunn

Chris Gabe

Data traces from four channels of an automated electrophoresis detection apparatus are aligned by identifying peaks in each of the four data traces; optionally normalizing the data traces to achieve a uniform peak height; combining the four data traces in an initial alignment; and determining coefficients of shift and stretch for selected data points within each data trace. The coefficients are determined by optimizing a cost function which reflects the extent of overlap of peaks in the combined normalized data traces to which the coefficients have been applied. The cost function is optimized when the extent of overlap is at a minimum. The coefficients are then used to generate a warp function for each data trace. These warp functions are applied to their respective data traces to produce four warped data traces which are aligned to form an aligned data set. The aligned data set may be displayed on a video screen of a sequencing apparatus, or may be used as the data set for a base-calling process.

Method and apparatus for alignment of signals for use in DNA base-calling

Nucleic acid polymers are sequenced by obtaining forward and reverse data sets for forward and reverse strands of a sample nucleic acid polymer. The apparent base sequences of these forward and reverse sets are determined and the apparent sequences are compared to identify any deviations from perfect complementarity. Any such deviation presents a choice between two bases, only one of which is correct. A confidence algorithm is applied to the peaks in the data sets associated with a deviation to arrive at a numerical confidence value for each of the two base choices. These confidence values are compared to each other and to a predetermined threshold, and the base represented by the peak with the better confidence value is assigned as the &ldquo;correct&rdquo; base, provided that its confidence value is better than the threshold. The confidence value takes into account at least one, and preferably more than one of several specific characteristics of the peaks in the data set that were not complementary.

Method for sequencing nucleic acids with reduced errors

Normalization of experimental fragment patterns for nucleic acid polymers having putatively known sequences starts with obtaining at least one raw fragment pattern for the experimental sample. The raw fragment pattern represents the positions of a selected nucleic acid base within the polymer as a function of migration time or distance. This raw fragment pattern is conditioned using conventional baseline correction and noise reduction technique to yield a clean fragment pattern. The clean fragment pattern is then evaluated to determine one or more &ldquo;normalization coefficients.&rdquo; These normalization coefficients reflect the displacement, stretching or shrinking, and rate of stretching or shrinking of the clean fragment, or segments thereof, which are necessary to obtain a suitably high degree of correlation between the clean fragment pattern and a standard fragment pattern which represents the positions of the selected nucleic acid base within a standard polymer actually having the known sequence as a function of migration time or distance. The normalization coefficients are then applied to the clean fragment pattern to produce a normalized fragment pattern which is used for base-calling in a conventional manner. This method may be implemented in an apparatus comprising a computer processor programmed to determine normalization coefficients for an experimental fragment pattern. This computer may be separate from the electrophoresis apparatus, or part of an integrated unit.

Method and system for DNA sequence determination and mutation detection

Electrophoretic separation of an analyte species in a sample is achieved with increased resolution by loading the sample onto a loading site of an electrophoresis gel, said loading site having a gel/buffer interface and then applying a focusing electric field to a first pair of electrodes to cause the analyte species to migrate to a narrow region disposed at or near the loading site to produce a focused sample. Then a separation electric field is applied to cause the analyte species in the focused sample to migrate through the electrophoresis gel and to be separated into bands. This method is preferably performed in an electrophoresis apparatus that is particularly adapted to practicing the method by virtue of the a pair of focusing electrodes which are positioned to cause migration of sample to a narrow region near the buffer/gel interface within the sample loading site of the gel. This actual location of this narrow region may be in a buffer region over the gel, or just within the gel near the loading site, for example within 500 microns of the loading site.

Method and apparatus for improving electrophoresis resolution

The sequence of a target nucleic acid polymer can be determined by (a) performing a first chain-extension sequencing reaction on the target nucleic acid polymer in a reaction mixture containing first and second chain-terminators to produce a first product mixture containing commonly-labeled polynucleotide fragments complementary to a first strand of the target nucleic acid polymer, each fragment in the mixture being terminated with the first or second chain-terminator; (b) performing a second chain extension sequencing reaction on the target nucleic acid polymer in a reaction mixture containing the first and a third chain-terminator to produce a second product mixture containing commonly-labeled polynucleotide fragments complementary to the first strand of the target nucleic acid polymer, each fragment in the mixture being terminated with the first or the third chain-terminator, said first, second and third chain-terminators each being different; and (c) evaluating the lengths of the polynucleotide fragments in the first and second product mixtures to determine the sequence of the target nucleic acid polymer. In the evaluation step, the first and second product mixtures can be evaluated in two separate lanes of a gel, in which case the labels employed in the two chain extension sequencing reactions can be the same. Alternatively, if the labels employed in the two chain extension reactions are different and spectroscopically distinguishable from one another, the first and second product mixtures can be combined before electrophoresis and the entire analysis can be performed in a single lane of a gel.

Method and apparatus for DNA-sequencing using reduced number of

Data traces from four channels of an automated electrophoresis detection apparatus are aligned by identifying peaks in each of the four data traces; normalizing the heights of the peaks in each of the data traces to a common value to generate four normalized data traces; combining the four normalized data traces in an initial alignment; and determining coefficients of shift and stretch for selected data points within each normalized data trace. The coefficients are determined by optimizing a cost function which reflects the extent of overlap of peaks in the combined normalized data traces to which the coefficients have been applied. The cost function is optimized when the extent of overlap is at a minimum. The coefficients are then used to generate a warp function for each normalized data trace. These warp function are applied to their respective data traces to produce four warped data traces which are aligned to form an aligned data set. The aligned data set may be displayed on a video screen of a sequencing apparatus, or may be used as the data set for a base-calling process.

Method and apparatus for alignment of signals for use in DNA

Normalization of experimental fragment patterns for nucleic acid polymers having putatively known sequences starts with obtaining at least one raw fragment pattern for the experimental sample. The raw fragment pattern represents the positions of a selected nucleic acid base within the polymer as a function of migration time or distance. This raw fragment pattern is conditioned using conventional baseline correction and noise reduction technique to yield a clean fragment pattern. The clean fragment pattern is then evaluated to determine one or more 'normalization coefficients.' These normalization coefficients reflect the displacement, stretching or shrinking, and rate of stretching or shrinking of the clean fragment, or segments thereof, which are necessary to obtain a suitably high degree of correlation between the clean fragment pattern and a standard fragment pattern which represents the positions of the selected nucleic acid base within a standard polymer actually having the known sequence as a function of migration time or distance. The normalization coefficients are then applied to the clean fragment pattern to produce a normalized fragment pattern which is used for base-calling in a conventional manner. This method may be implemented in an apparatus comprising a computer processor programmed to determine normalization coefficients for an experimental fragment pattern. This computer may be separate from the electrophoresis apparatus, or part of an integrated unit.

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Oakville, Canada

Rodney D Gilchrist