Gene conversion in nonsense suppressors of Schizosaccharomyces pombe. I. The influence of the genetic background and of three mutant genes (rad2, mut1 and mut2) on the frequency of the post-meiotic segregation.

Summary The frequency of gene conversion was assessed at the anticodon site of the sup3 gene of Schizosaccharomyces pombe. In order to detect a possible influence of the genetic background on the relative frequency of post-meiotic segregations amongst conversions, three similar crosses were analyzed which differed as follows: In cross I the two parents were derived by spontaneous mutation from one and the same strain. The heterogeneity of the genetic background between these two parent strains is assumed to be at a minimum level. In cross II the crossing partners were strains of the Bernese stock collection and differ probably in their genetic background to some extent. Last, in cross III, one of the parent strains was ten times repeatedly mutagenized with nitrosoguanidine in order to introduce cryptic mutations in the genome. A maximum degree of background heterogeneity between parents is expected for this cross. Neither the total conversion frequency nor the frequency of post-meiotic segregations amongst conversions were found to be significantly different in these three crosses.In addition, no effect of the radiation-sensitive mutation, rad2-44, and of two mutator mutations, mut1-4 and mut2-9, on the conversion pattern could be detected.