RNA plays a central, and until recently, somewhat underestimated role in the genetics underlying all forms of life on earth. This versatile molecule not only plays a crucial part in the synthesis of proteins from a DNA template, but is also intrinsically involved in the regulation of gene expression, and can even act as a catalyst in the form of a ribozyme. This latter property has led to the hypothesis that RNA - rather than DNA - could have played an essential part in the origin of life itself. This landmark text provides a systematic overview of the exciting and rapidly moving field of RNA biology. Key pioneering experiments, which provided the underlying evidence for what we now know, are described throughout, while the relevance of the subject to human disease is highlighted via frequent boxes. For the second edition of Molecular Biology of RNA, more introductory material has been incorporated at the beginning of the text, to aid students studying the subject for the first time.