Genomes

This chapter emphasizes on the structure and complexity of virus genomes. The chapter describes the diversity of virus genomes, and explains the major genetic mechanisms that affect viruses. The chemistry and structures of virus genomes are more varied than any of those seen in the entire bacterial, plant, or animal kingdoms. Virus genome structures and nucleotide sequences have been intensively studied in the recent decades because the power of recombinant DNA technology has focused a lot of attention in this area. The techniques of molecular biology have been a major influence on the virus genome. It is possible to separate the molecular analysis of virus genomes into two types of approaches: the physical analysis of structure and nucleotide sequence, and a more biological approach to examine the structure–function relationships of intact virus genomes and individual genetic elements. The chapter discusses virus genetics and its mutants, genetic and nongenetic interactions among viruses, small and large DNA genomes, positive and negative-strand RNA viruses, and segmented and multipartite virus genomes. Sequences and structures at the ends of virus genomes are in some ways functionally more significant than the unique coding regions within them. Common patterns of genetic organization seen in virus super-families suggest that many viruses have evolved from common ancestors and that exchange of genetic information among viruses has resulted in solutions to common problems.