Sanger sequencing, also known as the chain termination method, is a DNA sequencing technique that was developed by Frederick Sanger in the 1970s. It is a widely used method for DNA sequencing and was the first method used for large-scale sequencing projects such as the Human Genome Project. The Sanger sequencing method is based on the use of dideoxynucleotides (ddNTPs), which are modified nucleotides that lack the 3′-OH group needed for DNA chain elongation.

The Sanger sequencing process involves the following steps:

1. DNA fragmentation: The DNA of interest is first fragmented into smaller pieces using a restriction enzyme or by PCR amplification.
2. Primer annealing: A primer that binds to the DNA fragment is annealed to the template DNA at a specific location.
3. DNA synthesis: DNA polymerase is used to extend the primer by incorporating fluorescently-labeled dideoxynucleotides (ddNTPs) into the growing DNA strand. The incorporation of a ddNTP terminates DNA synthesis, resulting in a collection of fragments that vary in length by a single nucleotide.
4. Electrophoresis: The resulting fragments are separated by size using gel electrophoresis. The fragments are then detected using a fluorescent scanner, and the sequence is determined by analyzing the pattern of fluorescence.

Sanger sequencing is a highly accurate and reliable method for DNA sequencing, with an accuracy rate of up to 99.9%. However, it is limited by the length of DNA that can be sequenced in a single reaction, typically up to 800-1000 base pairs. The development of high-throughput sequencing technologies such as next-generation sequencing has largely replaced Sanger sequencing for large-scale sequencing projects due to its higher throughput and lower cost. However, Sanger sequencing remains a valuable method for verifying the accuracy of sequencing results and for sequencing smaller regions of DNA with high accuracy.