ABSTRACT
From a biological standpoint a more appropriate definition of viruses is that they are sub-microscopic intracellular parasites whose genetic material, consisting of either RNA or DNA, is packaged in a protective coat and transmitted from one host cell to another. The high efficiency in which viruses transmit and express their genetic material has led to viruses being adopted as gene transfer vectors. As viruses are relatively simple biological entities that are dependent upon the biochemical pathways of their host cells, the study of viral gene expression has resulted in fundamental breakthroughs in our understanding of the mechanisms of cellular gene expression. In addition to broadening our knowledge of transcription and post-transcriptional modification, the study of viruses has also led to breakthroughs in our understanding of translation, interferon action, major histocompatibility complex restriction and oncogenesis.
