ddNTPk

ddNTPk refers to dideoxynucleoside triphosphates modified with a fluorescent label. These modified nucleotides are crucial reagents in Sanger sequencing, a widely used method for determining the precise order of nucleotides in a DNA molecule. In Sanger sequencing, DNA polymerase is used to synthesize new DNA strands complementary to a template DNA strand. When a ddNTPk is incorporated into the growing DNA chain, it acts as a chain terminator because it lacks the 3' hydroxyl group necessary for further elongation. Each of the four ddNTPk (ddATP, ddTTP, ddCTP, and ddGTP) is labeled with a different colored fluorescent dye. This allows for the detection of the terminated fragments at each position in the DNA sequence. After the chain termination reaction, the fragments are separated by size using capillary electrophoresis. As the fragments pass a detector, the fluorescent signal corresponding to the terminal ddNTPk is read, revealing the nucleotide at that position. The sequence of these colored signals then represents the DNA sequence. The use of fluorescently labeled ddNTPk has significantly streamlined the Sanger sequencing process, enabling automated data collection and analysis, and making it a powerful tool in molecular biology research, diagnostics, and forensics.