ELEMENTS OF CHROMOSOME STRUCTURE AND FUNCTION IN FISSION YEAST

The investigation of fission yeast chromosome structure and function h as moved rapidly over the past 10 years. The isolation of replication origins, telomeres and centromeres has allowed the development of mini chromosomes, a yeast artificial chromosome (YAC)-like cloning system a nd investigations into chromosome segregation and behaviour during mit osis and meiosis. Many mutants have been isolated which are defective in chromosome segregation. The development of the fluorescent in-situ hybridization (FISH) technique for use in S. pombe has allowed the loc alization of centromeres and telomeres throughout mitosis and meiosis. In combination with indirect immunofluorescence to detect spindle and chromosomal proteins, the FISH technique should further advance our u nderstanding of fission yeast chromosome structure and function. The r ecent discovery of a heterochromatin-like structure mediating transcri ptional repression at centromeres reinforces the notion that fission y east centromeres are similar to those of larger eukaryotes. Further ch aracterization of such phenomena will accelerate the genetic dissectio n of this important chromosomal element.