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Special Article


ScienceAsia 4 (1978): 079-089 |doi: 10.2306/scienceasia1513-1874.1978.04.079

 

HEXAPLOID FORMATION THROUGH THE CONVERSION OF THE MATING- TYPE ALLELES BY THE ACTION OF HOMOTHALLIC GENES IN SACCHAROMYCES YEAST

 

VIPADA YOUTANANUKORNa and YASUJI OSHIMAb

Summary: Haxaploid breeding was attempted through the conversion of mating-type alleles by homothallic genes in triploid cells of Saccharomyces yeast homozygous for mating-type. To isolate triploid cells homozygous for mating-type efficiently. a procedure based on ultraviolet light induced reciprocal mitotic recombination monitored by homozygosity for thr4 (a recessive marker linked to the mating-type locus) was employed. Fifty-eight threonine dependent clones from Hq triploids and six threonine dependent clones from Hp triploids were isolated. Among those clones, five clones from Hq triplods were considered to be hexaploid because their cellular DNA content was about two times that of their respective parental triploids. However, the cell volume and the segregation of genetic markers did not accord well with the values expected for hexaploid cells. These presumably hexaploid clones produced smaIIer cells during vegetative growth. This may indicate mitotic reduction or segregation of unequal numbers of chromosomes to the daughter cells during mitotic cell division in the polyploid cells.

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a Department of Microbiology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
b Department of Fermentation Technology, Faculty of Engineering, Osaka University, Osaka. Japan

Received 1 May 1978