ddGTP (2',3'-Dideoxyguanosine-5'-triphosphate) is a modified nucleotide analog used primarily in Sanger DNA sequencing as a chain terminator. It incorporates into growing DNA strands during synthesis by DNA polymerase but lacks a 3'-OH group, halting further elongation and producing fragments of specific lengths for sequence determination. While not typically used in standard PCR amplification (which employs dNTPs), it is essential in cycle sequencing protocols. Additionally, ddGTP aids in studying DNA polymerase fidelity, enzyme kinetics, mutation mechanisms, and DNA repair processes. Its role in synthesizing terminated or modified DNA strands supports research in genetic functions and the design of antiviral nucleoside analogs for therapeutic applications.