Final answer:
Sanger sequencing is a DNA sequencing method where fluorescently labeled dideoxynucleotides are used to terminate DNA synthesis at various lengths, which are then identified by electrophoresis and a laser scanner to read the DNA sequence. It is accurate but can be slower than more modern methods.
Step-by-step explanation:
The principle behind Sanger sequencing, developed by Frederick Sanger, is known as the chain termination method. It involves synthesizing a complementary DNA strand from a single-stranded template using a mix of normal deoxynucleotides (dNTPs) and specially labeled dideoxynucleotides (ddNTPs). When a ddNTP is incorporated into the growing DNA strand, it prevents the addition of any more nucleotides, thus terminating the synthesis of that strand. The resulting DNA fragments of varying lengths are then separated by size through gel electrophoresis. Each fragment ends with a ddNTP that is labeled with a unique fluorescent dye, and the terminal base of each fragment can be identified using a laser scanner to create an electropherogram from which the DNA sequence is determined.
An advantage of Sanger sequencing is its high degree of reliability and accuracy. However, a limitation is that it sequences only one DNA strand at a time and looks for one base at a time, which can be time-consuming compared to newer sequencing techniques like next-generation sequencing (NGS).