ABSTRACT
The nucleic acid may be DNA or RNA, single-or double-stranded, but in any one virus is only of one type. In some of the smaller viruses, there is only sufficient nucleic acid to carry about ten genes (each gene carrying the information for the synthesis of one protein), although large viruses may contain the equivalent of several hundred genes. Clearly, in comparison with a bacterium, say, having a gene complement of 10,000 or more, viruses are genetically quite simple.
