DNA Sequencing

DNA sequencing is the molecular biology technique that determines the precise order of nucleotide bases- adenine, guanine, cytosine and thymine, in a given template, or fragment, of DNA. Sequencing is used by researchers in molecular biology or genetics laboratories to further scientific progress or is used clinically to make medical treatment decisions and aid in genetic counseling. Sequencing was described in 1977 by Maxim and Gilbert’s radiolabelling method, and further refined by Sanger’s chain termination method. The Maxim-Gilbert and Sanger manual techniques are used by smaller scale laboratories. Advances in automated sequencing equipment allowed the Human Genome Project to be completed ahead of schedule. Laboratories requiring higher throughput, longer sequence reads and faster turnaround times can utilize automated sequencers which process 96 or 384 samples at one time. A demand for low cost sequencing on a broader population level has driven the development of new high throughput technology, Next Generation Sequencing, which parallels the chain termination sequencing process. Considerations for sequencing equipment and reagents include the size and complexity of the DNA template, the required turnaround time, the validation process, the laboratory space and budget available, and the number of samples to be processed. Advances in sequencing provide for an appropriate technology for small, medium and high-throughput sequencing requirements.