In order to test the effects of a new drug, you isolate the messenger RNA molecules from both treated and untreated eukaryotic cells and separate them according to size, using gel electrophoresis. In each lane of the gel, the shorter RNA molecules migrate more quickly through the gel and end up near the bottom of the gel, whereas the longer RNAs migrate more slowly and remain near the top. The samples that were loaded into each of the four lanes are as follows: Lane 1: the primary RNA transcripts isolated from the nucleus of untreated cells.
Lane 2: the primary RNA transcripts isolated from the nucleus of cells treated with the drug being tested.
Lane 3: RNA isolated from the cytosol of untreated cells.
Lane 4: RNA isolated from the cytosol of cells treated with the drug being tested

Which conclusion is most likely to be correct?