ELECTROPHORETIC KARYOTYPE ANALYSIS OF YEAST SACCHAROMYCES CEREVISIAE
Zhu Yi-wen (Shanghai Institute of Cell Biology,Academic Sinica)
Analysis of electrophoretic karyotypes of several yeast (S.cerevisiae) strains by pulsed field gradient gel electrophoresis (PFGE) and Southern hybridization shows that: (1) muta-nts derived from the same original strain are identical or very similar in their electrophore-tic karyotypes,which may be a stable proper-ty of yeast; and (2) there are distinct diffe-rences among different strains,displaying chro-mosome-length polymorphisms (CLPs).CLPs may reflect disparities of chromosomal structu-res.The number of PFGE bands varies usually from 11 to 14 in strains we analysed. With their own karyotypes,yet these str-ains have some features in common: the distri-butions of their chromosomes (at least chro-mosome I-XVI) follow the same rule and,the electrophoretic mobilities of homologous chromosomes vary in a small range.A single PFGE band in some strains may be resolved into two or three in others because of CLPs.The former one,called doublet or triplet,is composed of two or three chromosomes of the latter.So we divide the electrophoretic karyo-type patterns of these strains into nine band-regions in according with their hybridizing be-havior.Bands in the same region can hybridi-ze with same (one or more) chromosome-specific probes.Two band-regions in CLP pat-tern,region 2 and 3,are more conservative. The chromosomal DNAs of the strain 7209-1A (a,WT) can be resolved into 18 bands by PFGE,exceeding the number of ch-romosomes in the yeast haploid genome.This unusual feature will be discussed in this paper.