Note: Ribosomal RNA

Ribosomes are the sites of protein synthesis in a cell. They are among the most fundamental organelles and are found both in procaryotes and eucaryotes, albeit in slightly different form. The cytoplasm of a procaryote contains tens of thousands of free-floating ribosomes.

Ribosomes are made up of both proteins and pieces of RNA. The ribosomes of procaryotes measure 70S (S = Svedberg unit; it describes the sedimentation rate during centrifugation, which depends on the size, weight, and shape of a particle). The 70S ribosome consists of two subunits--50S and 30S--each containing a variety of proteins and ribosomal RNA (rRNA) molecules. The smaller 30S subunit contains a 16S rRNA molecule and the larger 50S subunit contains a 5S and a 23S rRNA molecule.

This lab describes a technique to identify bacteria by using the sequence of the gene that codes for the 16S rRNA.