Introduction to DNA Sequencing

DNA sequencing methods were first developed more than 20 years ago with the publication of two approaches to sequencing methodology that became known as Sanger sequencing (1 ), based on enzymatic synthesis from a single-stranded DNA template with chain termination using dideoxynucleotides (ddNTPs) and Maxim-Gilbert sequencing (2 ), which involved chemical degradation of end-radio-labeled DNA fragments. Both methods relied on four-lane, highresolution polyacrylamide gel electrophoresis to separate the labeled fragment and allow the base sequence to be read in a staggered ladder-like fashion. Sanger sequencing was technically easier and faster, and thus became the main DNA sequencing method for the vast majority of applications.