What Makes Up DNA? An Explanation of DNA Composition, Including Polymers & Monomers

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DNA is a deoxyribonucleic acid. DNA is a nucleic acid that contains genetic instructions. This is used in the development and functioning of all known living organisms. The main role of DNA molecules is the long-term storage of information.

Chemically, DNA is a long polymer of simple units called nucleotides, with a backbone made of sugars and phosphate groups joined by diester bonds. Bases are the molecules attached to each other. Bases may be of A, T, G and C abbreviated as Adenine, Thymine, Guanine and Cytosine respectively. It is on these bases that DNA encode information. This information is read through genetic code, which specifies the sequences of amino acids within proteins.

The monomer units of DNA are nucleotides, and the polymer is known as polynucleotide. Each nucleotide consists of a 5-carbon sugar (deoxyribose), a nitrogen containing base attached to the sugar, and a phosphate group. Adenine and Guanine are purines. Purines are double ringed structures. Cytosine and Thymine are single ringed structures and are known as pyramidines. The deoxyribose sugar of the DNA has 5 carbons and 3 oxygens. Deoxyribose lacks hydroxyl group at the 2’ position when compared to ribose, the sugar component of RNA.

 A nucleoside is one of the four DNA bases covalently attached to the C1 position of a sugar. The sugar in ribonucleotides is ribose. Nucleosides differ from nucleotides in that they lack phosphate group. Nucleotide is a nucleoside with one or more phosphate groups covalently attached to the 3’ and 5’ hydroxyl groups.

The DNA backbone is a polymer with an alternating sugar-phosphate sequence. The deoxyribose sugar are joined at 3’ hydroxyl as well as 5’ hydroxyl groups to the phosphate groups with bonds known as phosphodiester bonds.

So, DNA consists of mainly sugar groups, phosphate groups, nucleotides such as Adenine, Guanine, Thymine and Cytosine. It is also considered as the genetic material in an organism.

Read more about DNA in What is DNA Made of? Part 2