A. Goffeau, * B. G. Barrell, H. Bussey, R. W. Davis, B. Dujon, H. Feldmann, F. Galibert, J. D. Hoheisel, C. Jacq, M. Johnston, E. J. Louis, H. W. Mewes, Y. Murakami, P. Philippsen, H. Tettelin, S. G. Oliver
Abstract
The genome of the yeast Saccharomyces cerevisiae has been completely sequenced through a worldwide collaboration. The sequence of 12,068 kilobases defines 5885 potential protein-encoding genes, approximately 140 genes specifying ribosomal RNA, 40 genes for small nuclear RNA molecules, and 275 transfer RNA genes. In addition, the complete sequence provides information about the higher order organization of yeast's 16 chromosomes and allows some insight into their evolutionary history. The genome shows a considerable amount of apparent genetic redundancy, and one of the major problems to be tackled during the next stage of the yeast genome project is to elucidate the biological functions of all of these genes.
The genome.
At the beginning of the sequencing project, perhaps 1000
genes encoding either RNA or protein products had been defined by genetic
analysis (20). The complete genome sequence defines some 5885 open reading
frames (ORFs) that are
likely to specify
protein products in the yeast cell. This means that a protein-encoding gene is
found for every 2 kb of the yeast genome, with almost 70% of the total sequence
consisting of ORFs (21). The yeast genome is much more compact than those of
its more complex relatives in the eukaryotic world. By contrast, the genome of
the nematode worm contains a potential protein-encoding gene every 6 kb (22), and in the human genome,
some 30 kb or more of sequence must be examined in order to uncover such a
gene. Analysis of the yeast genome reveals the existence of 6275 ORFs that
theoretically could encode proteins longer than 99 amino acids. However, 390
ORFs are unlikely to be translated into proteins. Thus, only 5885
protein-encoding genes are believed to exist. In addition, the yeast genome
contains some 140 ribosomal RNA genes in a arge tandem array on chromosome XII
and 40 genes encoding small nuclear RNAs (snRNAs) scattered throughout the 16
chromosomes; 275 transfer RNA (tRNA) genes (belonging to 43 families) are also
widely distributed. Table 2, which
provides details of the distribution of genes and other sequence elements among yeast's 16 chromosomes, shows that the genome has been completely sequenced, with the exception of a set of identical genes repeated in tandem.