Dideoxynukleotider

Dideoxynucleotides are a class of nucleotides that play a crucial role in the process of DNA sequencing, particularly in the Sanger sequencing method. They are structurally similar to standard deoxynucleotides (dNTPs) but lack a hydroxyl group (-OH) attached to the 3' carbon of the sugar ring. This absence of the 3' hydroxyl group causes DNA synthesis to terminate prematurely when a dideoxynucleotide is incorporated into the DNA strand.

Dideoxynucleotides are used as chain terminators because once they are incorporated into a growing DNA strand during DNA synthesis, the lack of the 3' hydroxyl group prevents the addition of any further nucleotides. This feature allows for the generation of DNA fragments of varying lengths, each ending with a dideoxynucleotide of a specific type—dideoxyadenosine (ddATP), dideoxycytidine (ddC), dideoxyguanine (ddG), or dideoxythymine (ddT).

The preparatory steps involve labeling the DNA fragments with a fluorescent dye attached to the dideoxynucleotides, which enables detection during electrophoresis. By running the resulting DNA fragments through a gel or capillary electrophoresis system, the sequence of nucleotides in the original DNA can be deduced based on the lengths and terminal bases of the fragments.

Because of their ability to produce accurate and reliable DNA sequence data, dideoxynucleotides are integral to genetic research, diagnostics, and biotechnology applications. Their development marked a significant advancement in molecular biology, enabling rapid and high-throughput sequencing of DNA molecules.