A FAMILY OF LABORATORY STRAINS OF SACCHAROMYCES-CEREVISIAE CARRY REARRANGEMENTS INVOLVING CHROMOSOME-I AND CHROMOSOME-III

In order to study meiotic segregation of chromosome length polymorphis m in yeast, we analysed the progeny of a cross involving two laborator y strains FL100trp and YNN295. Analysis of the parental strains led us to detect an important length polymorphism of chromosomes I and III i n FL100trp. A reciprocal translocation involving 80 kb of the left arm of chromosome III and 45 kb of the right arm of chromosome I was show n to be the cause for the observed polymorphism in this strain. The ch aracterization of the translocation breakpoints revealed the existence of a transposition hot-spot on chromosome I: the sequence of the tran slocation joints on chromosomes I and III suggests that the mechanism very likely involved homologous recombination between Ty2 transposable elements on each chromosome. Analysis of FL100, FL200 and FL100trp ur a, which are related to FL100trp, shows that this reciprocal transloca tion is present in some of the strains of the FL series, whereas the p arental strain FL100 does not carry the same rearrangement. We evidenc ed instead the duplication of 80 kb of chromosome III on chromosome I and a deletion of 45 kb of the right arm of chromosome I in this strai n, indicating that Secondary events might have taken place and that th e strain currently named FL100 is not the common ancestor of the FL se ries. (C) 1998 John Wiley & Sons, Ltd.