What conclusion can be drawn from comparing the samples in B and D?

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Enzyme Activity of an RNA Molecule

Source: Zang, A. J., T. R. Cech. 1986. The intervening sequence RNA of Tetrahymena is an enzyme. Science 231: 470–475.

Corresponding chapter(s) in the textbook: Chapter 2

Review the following terms before reading the paper and working on the problem: synthetic oligonucleotides, 32P radioisotope, 5′-end labeling, polyacrylamide gel electrophoresis, autoradiography

Read the paper and answer the questions below that refers to the data described in Figure 1 of the paper.

Be prepared to discuss the other experiments described in class.

Experiment

The function of an RNA molecule (designated L-19 IVS RNA) isolated from Tetrahymena thermophila (a ciliated protozoan often used as a model organism) was tested in vitro in this experiment. The samples in panel A did not contain L-19 IVS RNA; all other reaction mixtures contained equal amounts of L-19 IVS RNA and either 5′-end labeled (with 32P) pentacytidylate (an oligoribonucleotide consisting of five C-nucleotides; panels A and B), deoxypentacytidylate (an oligodeoxyribonucleotide consisting of five C-nucleotides; panel C), or hexauridylate (an oligoribonucleotide consisting of six U-nucleotides; panel D). The samples were free of proteins. Samples were incubated for the time periods indicated in the figure, then subjected to polyacrylamide gel electrophoresis followed by autoradiography. (The direction of electrophoresis was toward the bottom for each gel.)

Figure

Questions

1. How were the molecules in band a of panel B produced?

2. How were the molecules in band b of panel B produced?

3. What conclusion can be drawn from comparing the samples in A and B?

4. What conclusion can be drawn from comparing the samples in B and C?

5. What conclusion can be drawn from comparing the samples in B and D?

6. What is the function of L-19 IVS RNA? What enzyme activities are carried out by this RNA?

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