Numerous methods baaed on classical genetics have been developed for the genetic mapping of yeasts. Recombinant DNA technology and technology for electrophoretic separation of chromosomes make new approaches possible. The state-of-the-art in genetic mapping of Saccharmycea cerevkiae will be briefly reviewed. Then the availability and application of genetic mapping methods to non-conventional yeasts will be surveyed. Development of the genetic maps of the asexual diploid Candida a l b k n s and of the heterothallic yeast Yawowia lipolytim will be discussed in more detail.
Non-conventional yeasts excludes Smcharomyces cerevhiae and Schizmaecharomyces pombe, although the advanced genetic mapping techniques available for S. cerevisiae will be briefly discussed.
The ability t o determine genetic linkage and the availability of a genetic map are important for genetic and molecular studies and for the development of the industrial potential of a yeast. "Studies of recombination, regulation, and chromosome and gene isolation all are dependent on prior knowledge of the relative locations of various genes." (MORTIMER and TAVAF~ES 1976). For example, intra-versus intergenic complementation can usually be distinguished by linkage analysis. This review will begin with a brief up-date on the methods which have been developed for genetic mapping of s. cerevisiae, the yeast in which the most advanced genetic manipulations and analyses are possible. The development of classical mapping procedures and transformation systems for non-conventional yeasts will then be surveyed.
Development of genetic techniques and the genetic maps for Candida albicans and Yarrowia lipolytica will be covered in more detail. Candida albicans is a diploid organism and a sexual cycle has not been observed. Y . lipolytica is heterothallic and more amenable for genetic development. l ) Plenary lecture presented at the XIIth International Specialized Symposium on Yeast: "Genetics of non-conventional yeasts", held in Weimar, GDR, September 13-19, 1987 A project has also been initiated to construct a restriction map of total nuclear DNA from S. cerevdiae (OLSON et ul. 1986). The physical map will be useful in organizing the ever increasing amounts of molecular genetic data which is being accumulated, and the by-product of the project -clone collections which are cross-indexed t o physical mapswill facilitate structural and functional studies of specific local regions. Recently developed techniques for cloning large segments of DNA into yeast artificial chromosome vectors will also facilitate these studies (BURKE et al. 1987).
Classical genetic procedures and translormation systems of non-conventional yeasts
This section will concentrate more on the development of genetic procedures than on the specific development of genetic maps for nonconventional yeast. The genetic