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What are phosphodiester bonds in DNA and RNA?

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Diagram of a DNA polynucleotide chain showing linked deoxyribose sugars, phosphate groups, and nitrogenous bases (adenine, guanine, cytosine, thymine), with an inset comparing ribose and uracil in RNA. — Nucleic acid A portion of the polynucleotide chain of deoxyribonucleic acid (DNA), with an inset showing the corresponding pentose sugar and pyrimidine base in ribonucleic acid (RNA).

Phosphodiester bonds are the chemical linkages that connect successive nucleotides to form the backbone of both DNA and RNA molecules.1

In these polynucleotide chains, a phosphate group acts as a bridge, connecting the 5′-hydroxyl group of one pentose sugar to the 3′-hydroxyl group of the next sugar in the sequence. These bonds are identical in both DNA and RNA, providing the structural framework that holds the chain together.1

While these bonds are stable in DNA, the presence of a 2′-hydroxyl group on the ribose ring in RNA makes the phosphodiester bond in RNA more susceptible to cleavage, particularly in the presence of alkali. This chemical difference contributes to the relative instability of RNA compared to the more robust, double-stranded structure of DNA.23