Semi-automated Sanger sequencing was first described in 1977 by Sanger F. and with some improvements in the technique, remaining however conceptually unchanged it is used world-wide for clinical DNA sequencing. The method is based on the DNA polymerase-dependent synthesis of a complementary DNA strand in the presence of natural 2′-deoxynucleotides (dNTPs) and 2′,3′-dideoxynucleotides (ddNTPs) that serve as non-reversible synthesis terminators (Sanger F., 1997). The DNA synthesis reaction is randomly terminated whenever a ddNTP is added to the growing oligonucleotide chain, resulting in truncated products of varying lengths with an appropriate ddNTP at their 3′ end. The products are separated by size using polyacrylamide gel electrophoresis
