Description:
<jats:title>Abstract</jats:title><jats:p>Infectious RNA molecules lacking a protein coat have recently been shown to be the cause of several diseases in higher plants. These molecules, termed viroids, have been characterized as circular chains composed of about 360 nucleotide residues. They therefore comprise a class of infectious pathogens even smaller than viruses or bacteriophages. As a result of work on viroids it is now possible for the first time to give a complete description of the structure of a eukaryotic pathogen. Viroids possess structural and dynamic properties which have not as yet been observed with other nucleic acids. This article summarizes and discusses the results of predominantly biochemical and physicochemical studies on viroids.</jats:p>