Figure 5

Clonal variance in tSL RNA gene transcript. Histogram showing variations in steady state RNA levels and episomal DNA quantities for the uncloned pX-tSL transfectants (U) and the derived clonal lines (1–6). Relative RNA levels were quantified by poisoned primer extension and relative DNA levels were quantified by Southern blotting. The ratio of the episomal tSL RNA transcript to the genomic SL RNA transcript is plotted by the gray bar and the corresponding episomal:chromosomal using the left hand scale. The DNA ratio is plotted by the black bar using the right hand scale. The white bar plots the RNA ratio divided by the DNA ratio using the left hand scale. Assuming factors influencing steady state levels of RNA are equivalent between the all the transfectants, the white bar gives an estimate of the pX-tSL episome transcription activity per gene copy. The pX-tSL clonal lines exhibit different expression rates.