Dideoxynucleotide

Dideoxynucleotide is a type of nucleotide that is integral to the process of DNA sequencing. It is a modified form of a deoxynucleotide, which is a building block of DNA. The term "dideoxy" refers to the absence of two hydroxyl groups in the molecule, which are present in deoxynucleotides. This absence prevents the addition of further nucleotides, thus terminating DNA chain elongation.

Structure and Function

Dideoxynucleotides are structurally similar to deoxynucleotides, with the key difference being the absence of a hydroxyl group at the 3' carbon atom of the deoxyribose sugar. This absence is crucial as it prevents the formation of a phosphodiester bond necessary for the elongation of the DNA chain.

In the context of DNA sequencing, dideoxynucleotides are used in the Sanger sequencing method. During this process, a mixture of deoxynucleotides and a small proportion of dideoxynucleotides are added. When a dideoxynucleotide is incorporated into the growing DNA chain, it causes termination of the chain. By using dideoxynucleotides tagged with different fluorescent markers for each of the four bases, the sequence of the DNA can be determined.

Applications

Beyond DNA sequencing, dideoxynucleotides also have therapeutic applications. Certain types of dideoxynucleotides, such as Zidovudine (AZT), are used as antiretroviral therapy for the treatment of HIV/AIDS. These drugs work by inhibiting the action of reverse transcriptase, an enzyme that HIV uses to replicate its genetic material.

See Also

• Nucleotide
• DNA sequencing
• Sanger sequencing
• Zidovudine
• Antiretroviral therapy