dideoksinukleotidi

Dideoksinukleotidi are synthetic analogs of deoxynucleotides, the building blocks of DNA. The key difference lies in the absence of a hydroxyl group at the 3' position of the sugar ring, hence the name "dideoxy." This structural modification has profound implications for DNA synthesis. When a dideoksinukleotidi is incorporated into a growing DNA chain by DNA polymerase, it terminates further elongation. This is because DNA polymerase requires a free 3'-hydroxyl group to attach the next incoming nucleotide. Without it, the chain cannot be extended. This chain-terminating property makes dideoksinukleotidi invaluable tools in molecular biology, particularly in the Sanger sequencing method, also known as dideoxy sequencing. In Sanger sequencing, a mixture of the four standard deoxynucleotides and a small amount of one type of dideoksinukleotidi (labeled with a fluorescent dye or radioactive isotope) is used to synthesize DNA fragments. Each dideoksinukleotidi terminates the growing chain at different positions, creating a set of DNA fragments of varying lengths. These fragments are then separated by size, and the incorporated dideoksinukleotidi at the end of each fragment reveals the sequence of the original DNA. Dideoksinukleotidi are also used in antiviral therapies, such as in the treatment of HIV. By being incorporated into the viral DNA, they halt its replication.