The genetic and physical maps of the sixteen chromosomes of Saccharomyces cerevisiae are based on data presented in Mortimer et al. in preparation (1995) as well as on data presented in earlier reviews (Mortimer and Schild, Microbiol. Rev. 44:519-571 (1980), Microbiol. Rev. 49:181-213 (1985), Mortimer et al., Yeast 5:321-404 (1989), and Mortimer et al., Yeast 8:817-902 (1992). Physical maps were compiled from Riles et al., Genetics 134:81-150 (1992), Riles et al., unpublished data, gene/clone associations reported by many laboratories, and DNA consensus sequences produced by Fred Dietrich from GenBank sequences, and the seven completed yeast chromosomal sequences: I, II, III, V, VIII, IX, and XI (Bussey et al., (1994); Feldmann et al, (1994), EMBL J. in press; Oliver et al. (1992), Nature 357:38-46; Dietrich et al., (1994); Johnston et al., (1994), Science 265:2077-2082 Barrell et al., (1994); Dujon et al. (1994), Nature 369:371-378). All the information in these figures derives directly from the electronic database maintained by the Saccharomyces Genome Database Group at Stanford. Genetic maps are drawn as solid vertical lines; to scale or dashed lines representing linkages established by mitotic crossing over. Centromeres are represented as circles on the genetic map line with the left arm above and the right arm below the centromere. Physical maps are drawn parallel and to the left of the genetic maps Q distinguished by the scale (in kb) to the left of this line. Horizontal tick marks to the right of the genetic map lines indicate the positions of the genes; in crowded regions, these tick marks are joined to the gene symbol by a thin connecting line. Symbols by the physical map represent genes located solely by physical methods. Note that two loci (RDN1 on XII and CUP1 on VIII are known to vary greatly in length from strain to strain. Dashed lines connect the same gene on the genetic and physical maps, only a fraction of such associations are shown. Crowded regions on the genetic map are drawn as expansions. Genes added since Edition 11 are in bold type. Genes that have been mapped on the basis of sequence overlap relative to genetically-mapped genes are positioned to the left of the genetic map line and are connected to this line by tick marks; when the order of these genes relative to the mapped genes is unknown, they are arbitrarily placed distal to the mapped gene. Genes listed below the chromosome maps or expanded regions of these maps have been assigned to the chromosome or region either by genetic or physical methods but have not been positioned more precisely. Some gene symbols in this category are capitalized; this does not necessarily indicate dominance but instead means that the wild type copy was used to map the gene. With this edition the numerous synonyms have not been included. With this edition we have chosen just one symbol for each gene to show on the maps. The symbols all remain in the underlying database. The choice of symbol was guided by an amalgam of consensus, literature usage, clarity relative to function, and priority in the literature. Many of the physical map gene positions are based on hybridization results to the prime clone filter grids. In these cases the location of the gene is arbitarily placed at the center of the hybridizing region. New information on gene mapping or gene name registration should be sent to the Saccharomyces Genome Database Group (FAX: 415-726-7016, electronic mail: email@example.com).