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. 2011 Sep;189(1):37–53. doi: 10.1534/genetics.111.130187

Figure 5 .

Figure 5 

β-Galactosidase activity of the Pur-Lac tester strain derivatives. The low LacZ level in the tester depends on the combined effects of operon repression and the polar effect of the purD UGA mutation. The terminator stem has a small effect in the absence of the purD UGA mutation (compare the first two strains) and a large effect in strains with the UGA mutation (compare the third and forth strains). Single mutants and purR, purO double mutants have a partially Lac+ phenotype under selective conditions on the reversion plate. Double mutants at the far left are fully Lac+. Strains assayed, in order of vertical bars, were: T12306 (No UGA, mDEL+), TT26208 (No UGA, mDEL1), TT25154 (tester strain UGA, mDEL1+), TT26174 (mDEL1 single), TT26176 (purO single), TT26169 (purR single), TT26209 (purR, purO), TT26175 (purO, mDEL1), and TT25177 (purR, mDEL1).