DNA sequencing is an essential procedure in many fields of study, e.g. for determination of unknown sequences, checking the accuracy of DNA sequences from cloned genes or PCR products intended for further cloning. Today there are several companies who perform this service. SeqWright is based in Houston, Texas, and was founded in 1994. Since then, it has grown into one of the largest companies providing custom DNA sequencing and related services (e.g. SNP genotyping, library construction, primer walking, EST sequencing, gene mapping and mutagenesis, cloning, Southern blotting, siRNA vector constructions, DNA microarray expression analysis). Clients are from research institutions, universities and pharmaceutical companies in America and Europe. Since 1998, SeqWright has provided high-throughput cDNA sequencing services and has been involved in sequencing of several unique cDNA libraries, e.g. Zebra Fish brain full-length cDNA library.
SeqWright offers standard DNA sequencing service for single-tube and high-throughput (microtiterplate). The DNA sequencing is based on the fluorescent dye-termination method using the ABI Prism 3730xl DNA sequencer. They validate the DNA sequence by applying a base call quality (Q) scoring, where good scores are characterized by strong, consistent peaks, good color separation, uniform peak spacing, and good peak shape at the base call location. Typically, over 650 bp can be read with a minimum score of Q20. Primers for sequencing can be either synthesized by SeqWright according to the customer’s sequence information or provided by the customer. Universal primers are also available from the company (a list of primers is provided on their website). Before placing an order, it is recommended that you contact SeqWright to discuss the project, obtain pricing information and a quotation, valid for one year for the same project. Order forms (available as PDF files from their website) containing contact and purchasing information, DNA and primer information have to be sent together with the DNA and/or primer samples. SeqWright’s website lists the requirements for concentration and amount of DNA and primers, e.g. plasmid DNA (<6 kb): 40-60 ng/µl, 8 µl (total amount approx. 500 ng). Plasmid cDNA can be isolated by miniprep, but SeqWright recommends that DNA concentration and purity should be analyzed; purer DNA ensures higher quality sequencing. Sequencing results are usually available 24 hours after the sample was received at SeqWright; results can be sent via e-mail or accessed through a password protected web download.
We have used SeqWright’s service for several years for sequencing DNA vectors and for sequencing an unknown genomic sequences cloned into a commercial sequencing vector. I usually shipped the samples overnight at room temperature; if I sent samples on Friday, I made sure that they could be received on Saturday. Usually, I obtained my results via e-mail at the end of the next day, or if re-sequencing was necessary the day after. In some cases, I was able to accurately read up to 900 bp with the cloned genomic DNA. Initially, I ordered sequencing reactions from both sides of the cloned insert, but realized that the sequences were identical, even from 2 different clones. I then discussed my project with technical service and indicated that I needed as much DNA sequence information as possible from my unknown genomic DNA. They programmed the sequencing conditions accordingly and I could then reliably read approximately 900 bp of my cDNA sequence. In order to get my whole sequence in one run, I only needed to sequence in one direction, but used two different clones to confirm the sequence.
For fast and reliable high quality sequencing, I recommend using SeqWright’s service. I was amazed by their ability to sequence DNA sequences quickly and with high accuracy and at the same time optimizing the length of the reading frame. The customer and technical service were exceptionally helpful and provided me with all information I needed. After discussing my project with them, they told me the best way to send my samples and how to obtain the best sequencing results.