A major structural and functional component of the ribosome, which builds proteins in a cell, is 16s rRNA, or 16s ribosomal nucleic acid. The ribosome has a small subunit and the large subunit, both of which are made up of various types of rRNA and proteins that associate with the rRNA to help it function more efficiently. Most of the small subunit is composed of 16s rRNA. This RNA has two major functions, to make proper connections between the subunits and to ensure that the protein created by the ribosome is accurate. Its structure and function is highly conserved between varied types of organisms.
Ribosomes build proteins based on a system similar to a mechanical assembly line, and all of this functionality is handled by 16s rRNA. The RNA contains three pockets which, in order, bring in the building blocks of proteins, connect them to the growing protein, then eject the used pieces to prepare for making the next connection. This process sounds simple, but it is tightly controlled and must be very precise. A mistake in any of these steps can cause proteins to be built incorrectly, which can cause many levels of genetic disease. Since all organisms rely to some degree on proteins, the important function of protein building almost always relies on 16s rRNA.
The structure of 16s rRNA does not need to be exactly the same among organisms, although its function does. Between species, and even within a single organism, the exact sequence of nucleic acids in a particular RNA molecule can vary without any detriment to the organism. Often, multiple locations in the sequence will vary, but that is not always the case. These variations are called ribotypes. They are of particular interest when studying the ecology and evolution of single celled organisms like bacteria.
16s rRNA is often used as a molecular marker, where its sequence and structure are analyzed to determine the degree of change between species, particularly bacteria. Its data is often used to build phylogenetic trees, which are diagrams of possible relationships between species. The high conservation of RNA between species makes differences all the more apparent. Ribotypes may help or hinder this type of research, because they may mark a significant change, but also may be just an organism-specific RNA variation. The research can be used to predict evolution of microorganisms or develop drug targets to prevent bacteria from making proteins they need to survive, so it has direct applications to human health.