What holds the monomers of a single strand of nucleic acid together in a chain?

Nucleic acids are of two types DNA and RNA which are made up of monomeric units called nucleotides.

One monomer is one nucleotide which further consists of three parts:

1: Nitrogenous base

2: Sugar (a ribose sugar in RNA and a deoxyribose sugar in DNA)

3: Phosphate group

Explanation:

If we talk about single strand of nucleic acid DNA or RNA, there is a phosphodiester linkage that holds monomers together in a strand of nucleic acids. This phospho di ester linkage is formed when a condensation reaction occurs between a hydroxyl group of two sugars and a phosphate group.

You can see a better representation in attached figure.

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