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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.