An example of identification and analysis of conditional alleles

(a) Treat with mutagen Temperature-sensitive utant \O ”a I O WK“ \ , w w Plate " ‘39 Replica " ‘59 Haploid yeast Yeast colonies Yeast colonies grown at 23°C at 23°C at 36°C _‘ : Temperature-sensitive (ts) mutants grow at : 23°C but not at 36°C. (b) Yeast-cell cycle phenotype QL a; ,_ , . , cdc gene cdc28 cdc6, 7, 8, 16, cdc15 number 17, 20, 23 I Phenotypes of cell division cycle (cdc) mutants resemble those of wild-type yeast at (c) Specific cellular biological processes blocked in cdc mutant lines suggest specific cell cycle functions for the mutated genes. Spindle pole Initiation DNA DNA Nuclear body of DNA synthesis synthesis division duplication synthesis checkpoint (mitosis) m i l l l —>#—>-—+—>—-> cdc28 cdc? cdc‘6, 8, 17 cdc16, 20, 23 cdc15