Fig. 4. (A) Determination of the relative growth rates of Dd-STATb- and Dd-STATb+ cells. A co-cultivation experiment, with three cycles, was performed using a mixture of Dd-STATb- and Dd-STATb+ cells that were derived from a single transformation with the Dd-STATb disruption construct (see text). The cells were allowed to grow to saturation (2x10⁷/ml) and then diluted 1 in 100 for regrowth. (B) A compilation of five co-cultivation experiments. The first (top) experiment is that described in A and the other four experiments were performed in the same way. Although the rate of loss of the null cells was variable, the outcome was reproducible; the random integrant cells always came to dominate the population.