Those PCR products yielding a single, bright amplification band were prepared for cycle sequencing by cleaning the PCR product using an ExoSAP-IT™ kit (USB Corporation). We used 7 ll of PCR product, 2 ll of ExoSAP solution (0.1 ll exonuclease at a stock concentration of 1 U/ll and 1.9 ll of SAP buffer at a stock concentration of 20 U/ll) and 1 ll of 10 SAP buffer. Cleanup reactions involved incubating this mixture at 37 C for 60 min followed by heating to 80 C for 15 min to denature the exonuclease and phosphatase enzymes. Three to five microliters of the purified PCR product were then used as a template for cycle sequencing of the entire amplicon in overlapping heavy and light strand fragments of 700 base pairs using ABI BigDye™ 3.1 Terminator sequencing chemistry. Sequencing reactions were performed in a total volume of 10 ll containing 1 ll of Big Dye™, reaction mix, 1.5 ll of 5 Big-Dye™ reaction buffer, 3.3 pmol of a particular sequencing primer,1–4 ll of ExoSAP-treated template (depending on the quality of the PCR product), and water up to a total volume of 10 ll. The cycle sequencing reaction consisted of 25 cycles of denaturing at 96C for 10 s, primer annealing at 50C for 5 s, and extension at 60C for
4 min. Cycle-sequencing products were purified via ethanol precipitation and re-suspended in 10 ll of Hi-Di formamide and then separated and visualized via capillary electrophoresis on an ABI
3730 DNA Analyzer (Applied Biosystems). Raw sequencing traces were imported into Sequencher 3.1 (Gene Codes Corporation) and edited to trim low quality base calls from flanking regions.
All sequences were visually checked for miscalls due to either bad base spacing or over-fluorescence of particular dye nucleotides and were then assembled into locus specific contigs using the software Sequencher 3.1 (Gene Codes Corporation). As a check against
possible inadvertent inclusion of nuclear mitochondrial pseudogene (or ‘‘numt’’) sequences instead of true mtDNA sequences in our dataset, we confirmed that our initial long-range amplifications yielded a single PCR band of expected size and that within each coding region, all sequences were free of frame shift errors and unexpected termination codons. We also confirmed that no sequences yielded unexpected phylogenetic placement in locusspecific
or overall phylogenetic analyses.
Those PCR products yielding a single, bright amplification band were prepared for cycle sequencing by cleaning the PCR product using an ExoSAP-IT™ kit (USB Corporation). We used 7 ll of PCR product, 2 ll of ExoSAP solution (0.1 ll exonuclease at a stock concentration of 1 U/ll and 1.9 ll of SAP buffer at a stock concentration of 20 U/ll) and 1 ll of 10 SAP buffer. Cleanup reactions involved incubating this mixture at 37 C for 60 min followed by heating to 80 C for 15 min to denature the exonuclease and phosphatase enzymes. Three to five microliters of the purified PCR product were then used as a template for cycle sequencing of the entire amplicon in overlapping heavy and light strand fragments of 700 base pairs using ABI BigDye™ 3.1 Terminator sequencing chemistry. Sequencing reactions were performed in a total volume of 10 ll containing 1 ll of Big Dye™, reaction mix, 1.5 ll of 5 Big-Dye™ reaction buffer, 3.3 pmol of a particular sequencing primer,1–4 ll of ExoSAP-treated template (depending on the quality of the PCR product), and water up to a total volume of 10 ll. The cycle sequencing reaction consisted of 25 cycles of denaturing at 96C for 10 s, primer annealing at 50C for 5 s, and extension at 60C for4 min. Cycle-sequencing products were purified via ethanol precipitation and re-suspended in 10 ll of Hi-Di formamide and then separated and visualized via capillary electrophoresis on an ABI3730 DNA Analyzer (Applied Biosystems). Raw sequencing traces were imported into Sequencher 3.1 (Gene Codes Corporation) and edited to trim low quality base calls from flanking regions.All sequences were visually checked for miscalls due to either bad base spacing or over-fluorescence of particular dye nucleotides and were then assembled into locus specific contigs using the software Sequencher 3.1 (Gene Codes Corporation). As a check againstpossible inadvertent inclusion of nuclear mitochondrial pseudogene (or ‘‘numt’’) sequences instead of true mtDNA sequences in our dataset, we confirmed that our initial long-range amplifications yielded a single PCR band of expected size and that within each coding region, all sequences were free of frame shift errors and unexpected termination codons. We also confirmed that no sequences yielded unexpected phylogenetic placement in locusspecificor overall phylogenetic analyses.
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