MAPPING AND GENE CONVERSION STUDIES WITH THE STRUCTURAL GENE FOR ISO-1-CYTOCHROME C IN YEAST

[摘要] We have investigated the order of the four genes cyc1 , rad7 , SUP4 , and cdc8 which form a tightly linked cluster on the right arm of chromosome X in the yeast Saccharomyces cerevisiae . Crossing over and coconversion data from tetrad analysis established the gene order to be centromere– cyc1 – rad7 – SUP4 . Also cdc8 appeared to be distal to SUP4 on the basis of crossovers that were associated with conversion of SUP4 . The frequencies of recombination and the occurrence of coconversions suggest that these four genes are contiguous or at least nearly so. Gene-conversion frequencies for several cyc1 alleles were studied, including cyc1 – 1 , a deletion of the whole gene that extends into the rad7 locus. The cyc1 – 1 deletion was found to be capable of conversion, though at a frequency some fivefold less than the other alleles studied, and both 3:1 and 1:3 events were detected. In general 1:3 and 3:1 conversion events were equally frequent at all loci studied, and approximately 50% of conversions were accompanied by reciprocal recombination for flanking markers. The orientation of the cyc1 gene could not be clearly deduced from the behavior of the distal marker SUP4 in wild-type recombinants that arose from diploids heteroallelic for cyc1 mutations.

[学科分类] 医学（综合）