Briefly contrast the dideoxy DNA sequencing developed by Fred Sanger with pyrosequencing methods. ...

Dideoxy DNA sequencing involves use of altered (dideoxy) nucleotides that cause termination of replication at each site where such a nucleotide is inserted. The pyrosequencing method does not require chain termination. All four deoxynucleotide precursors are present at all times in the dideoxy sequencing reaction, whereas, only one is present at a time in the pyrosequencing reaction. The DNA template is immobilized on a bead in pyrosequencing, and the method of detection is the production of light by utilizing the pyrophosphate produced after the incorporation of a nucleotide. In the dideoxy method, the DNA template is not immobilized and the sequence is read with the help of fluorescent dyes attached to the dideoxy nucleotide molecules.