Practice question

Question

Normal yeast cells grow at 42°C. Five yeast haploid strains, with independent alleles of YFG1 having impaired cell growth at 42°C, were isolated and labeled as yfg1ts1 to yfg1ts5. A haploid (yfg1ts1) carrying a spontaneously generated mutation (sup1) at an independent locus was isolated, which can grow at 42°C. Using pairwise crossing, sup1 was introduced into strains carrying yfg1ts2 to yfg1ts5 alleles. All these haploids grew at 42°C. Based on this data, the following statements were made to describe the Sup1-Yfg1 molecular/genetic interaction. A. Sup1 codes for a protein which, when over-expressed, stabilized mutant yfg1ts proteins. B. Sup1 codes for a protein that physically interacts with Yfg1 protein. C. Sup1 protein upregulates an alternate pathway. D. Sup1 is a nonsense suppressor that restores protein translation in cells carrying yfg1ts allele. Which one of the following options represents the combination of all correct statements?