Activity of strong Chi alleles in RecC tunnel mutants. Shown are results of type 2 crosses (Figure 3C) with two χ⁺L alleles that have the same 5′ flanking sequence as χ⁺L251 but different 3′ flanks (Table 2), which confer high Chi activity in recBCD⁺ cells (Taylor et al. 2016). The Chi octamer mutant χ⁻L259 was used as a control, as were the recBCD null mutant recB21 and the recD1013 mutant, in both of which Chi is inactive (Stahl and Stahl 1977; Amundsen et al. 1986). Data for recBCD⁺ and recB21 are from Taylor et al. (2016).