Cover photograph (Copyright © 2003, American Society for Microbiology. All Rights Reserved.): Electron micrograph of rRNA genes from a Saccharomyces cerevisiae strain containing only ~42 rRNA genes. Wild-type strains have ~140 rRNA genes. The reduced-copy-number strain grows as well as control strains by loading twice as many polymerases per active rRNA gene, indicating that RNA polymerase I transcription is not limited by the number of active genes in normal cells during exponential growth. (See related article on p. 1558.)