Sanger dideoxy sequencing method utilizes base-specific termination during in vitro synthesis of DNA. The basis for terminating the elongation of the DNA chain is the use a nucleoside triphosphate containing a ribose sugar reduced in both the 2 and 3 positions (ddNTP). When four normal dNTPs (one of them is labeled at its a position with 32P or 35 S) are mixed with the respective ddNTP in four different reaction tubes chain termination that ended in nuclitide A C G and T will occur. When products are analyzed radioactive signals will be achieved for all bands on the ladder gel.