Characterisation of mutant strainThe mutant strain cdc9--50 was isolated from wild-type S. pombe (972h.. obtained from U. Leupold,Bern) after nitrosoguanidine mutagenesis (P. Nurse and B. Carter, un- published). When grown at 35oc, cells of strain cdc9-50 divide at ahout half the volume of wild-type cells at that temperature(Tahle \). The mutant phenotype is tempera- ture-enhanced since at 25 oc cdc9-50 divides at a cellvolume only 15'X. smaller than wild type (Table I). These differences are also reflected in the RNAand protein con- tent per cell in exponentially growing cultures of the two strains at the twotemperaiures (Table I). Thus cdc9-50 divides at both a lower cell colume and a reduced macro-molecular content compared with wild type. In spite of these differences cdc9-50 has a similargeneration time to wild type at both 25 "C and 35 oc (Table 1).The mutant phenotype of reduced cell size at division segregated 2:2 in all of 27 asci dissected froma wild-type 975 h+ x cdc9- 50h- cross (P. Thuriaux, personal communica- tion), demonstrating that itis caused by a mutation in a single nuclear gene.Table 1 Characteristics of wild type and mutant at 25 C and 35 CCell volume atcell division(µm³)MeanCell volume atnuclear division(um³)MeanGrowth temperature(°C)Macromolecularcontent per cellStrainGeneration time(min)s.d.s.d.ProteinRNA(pg per cell) (pgper cell)Wild-type9722281421291499.16.41211398.49.012.414.12.542.9035Mutantcde9-5023213810972.78.87.898.060.47.98.49.661.162.261.541.Why did they suspect it was caused by a single gene mutation?

Name: Characterisation of mutant strainThe mutant strain cdc9--50 was isola
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Description: Characterisation of mutant strainThe mutant strain cdc9--50 was isolated from wild-type S. pombe (972h.. obtained from U. Leupold,Bern) after nitrosoguanidine mutagenesis (P. Nurse and B. Carter, un- published). When grown at 35oc, cells of strain c