Ribosomes are the universal ribonucleoprotein particles that translate the genetic code into proteins. They are built of two subunits that associate upon initiation of protein synthesis. Typical eubacterial ribosomes (70S) consist of 57 different molecules (3 rRNAs and 54 proteins) and can dissociate into a small (30S) and a large subunit (50S). The small subunit is responsible for the formation of the initiation complex, performs the decoding of the genetic information, and controls the fidelity of codon-anticodon interactions. The large subunit catalyzes the peptide bond formation and provides the path for the nascent polypeptide chain.

The section (or gene) that codes for ribosomal RNA in a cell is the 16S rRNA gene (or rDNA gene).

• Every cell has a 16S rRNA gene as the ribosomal RNA (rRNA) is an integral part of the ribosome, which is responsible for making cellular proteins.
• This gene is only about 1550 bp in length in prokaryotes and every cell has from one to more than 25 copies of this gene.
• The 16S rRNA molecule folds itself into a shape that must fit like a puzzle piece with other molecules and consequently, some structural elements must be maintained.
• Therefore, some sections of the sequence may vary and others may not.