Figure 3.

Comparison of Tec element chromatin in the micronucleus with that of the anlagen. Total nuclei from vegetative cells (micronuclei and macronuclei) and the combination of developing macronuclei (anlagen) and old macronuclei from cells at 43 h of development were treated at 37°C with MNase at several concentrations of enzyme (0.05, 0.25, or 1.25 U/ml) and for varying times (10, 30, or 45 min), as shown above each lane. The DNA was isolated, electrophoresed in 1.5% agarose, Southern blotted, and then probed consecutively with a Tec element probe (the 1-kb EcoRI fragment from Tec1, shown in Figure 2), the mac-specific probe, and the 0.8-kb EcoRI fragment from the macronuclear rDNA molecule (only the vegetative samples are shown for the rDNA probe). Samples from nuclei incubated for 45 min without the addition of MNase, to control for endogenous nuclease activity, are shown for comparison (lanes E). The marker lanes shown are 100- and 123-bp ladders.