Question: In the capping of mRNA by the enzymes involved in that process, the last step in cap addition is the methylation of the cap guanosine residue at the 7-position forming 7-me-G. You make a conditional mutation in the gene encoding this enzyme in yeast which prevents the cells from growing at 37 °C, but which functions properly at 30 °C. In cells growing at 37 °C, you test for the cap structure at the 5' end of mRNAs and show that not only do they not have the 7-me-G modification, but the expected GpppX cap is actually ppX. You also show that the RNA triphosphatase and guanylyltransferase enzymes are able to function properly at this higher temperature. Provide a good biochemical hypothesis for why the cap is absent in this strain of yeast. Need Assignment Help?