- The cluster variants were based on different combinations of promoters, upstream activating sequence elements, introns, spacers, and terminators (Fig. 3). The cell populations were analysed for the presence of the four cluster genes pfa1, pfa2, pfa3, and ppt after culturing for two weeks. For each strain, 40 clones were analysed using PCR, and a set of eight specific primers allowed us to test for the presence of all genes simultaneously. The obtained patterns provided the cluster configuration for each clone and population-based insight into the frequency of different mutation events, which are given as relative fractions in percent
