Eukaryotic Transcription

Free Response

A scientist observes that a cell has an RNA polymerase deficiency that prevents it from making proteins. Describe three additional observations that would together support the conclusion that a defect in RNA polymerase I activity, and not problems with the other polymerases, causes the defect.

Hint:

To determine that a RNA polymerase I mutation or deficiency is causing the defect in protein production, the scientist would need to make observations that provide evidence that RNA polymerases II and III are working in the cell. The observations eliminating RNA polymerase II as the defect could include:

  • Transcription of mRNAs in the nucleus;
  • Presence of processed mRNAs in the cytoplasm

The observations eliminating RNA polymerase III could include:

  • Isolation of small nuclear RNAs from the cell;
  • Isolation of microRNAs from the cell;
  • Transcription of 5S rRNA in the nucleus;
  • Presence of tRNAs in the cytoplasm

The observations implicating RNA polymerase I could include:

  • A lack of functional ribosomes in the cytoplasm (RNA polymerase I or III);
  • A lack of RNA polymerase I protein;
  • RNA polymerase I protein is non-functional