How is nitrogen used to make DNA and RNA?

Nitrogen is a fundamental component of DNA and RNA because it forms the essential nitrogenous bases that carry genetic information. These molecules are built from repeating units called nucleotides, each consisting of a phosphate group, a sugar, and a nitrogen-containing base.123

The nitrogenous bases are categorized into two groups:
* Purines: Adenine (A) and guanine (G), which are found in both DNA and RNA.42
* Pyrimidines: Cytosine (C), thymine (found only in DNA), and uracil (found only in RNA).42

In the structure of DNA, these nitrogen-containing bases act as the "rungs" of the double helix ladder. They pair specifically—adenine with thymine, and guanine with cytosine—via weak hydrogen bonds, which stabilize the molecule while allowing the strands to separate for replication. Because most organisms cannot use atmospheric nitrogen directly, they rely on nitrogen fixation by bacteria and archaea to convert it into usable compounds like ammonia and nitrates, which eventually enter the food chain to support the synthesis of these vital genetic materials.251