dideoxynukleotidokkal

Dideoxynucleotides, often abbreviated as ddNTPs, are modified nucleoside triphosphates that play a crucial role in molecular biology, particularly in DNA sequencing and synthesis. Unlike natural deoxynucleotides (dNTPs), dideoxynucleotides lack a hydroxyl group at the 3' carbon of their deoxyribose sugar. This seemingly small structural difference has significant implications for DNA polymerization.

During DNA synthesis, a DNA polymerase enzyme adds new nucleotides to the growing DNA strand by forming a phosphodiester bond between the 3' hydroxyl group of the last nucleotide in the chain and the 5' phosphate group of the incoming nucleotide. When a dideoxynucleotide is incorporated, the absence of the 3' hydroxyl group prevents the formation of this phosphodiester bond. Consequently, DNA chain elongation is terminated at that point.

This chain-terminating property is the basis of the Sanger sequencing method, also known as the dideoxy chain-termination method. In this technique, a DNA template is replicated in the presence of a DNA polymerase, a mixture of all four dNTPs, and a small amount of one specific ddNTP (either ddATP, ddTTP, ddGTP, or ddCTP). Each reaction tube contains a different ddNTP. When a ddNTP is randomly incorporated, it halts the synthesis of that particular DNA fragment. By separating the resulting DNA fragments by size, researchers can determine the order of nucleotides in the original DNA sequence. Dideoxynucleotides are essential tools for understanding genetic information.