Accumulation of large non-circular forms of the chromosome in recombination-defective mutants. A: In an otherwise rec+ background. The mutation alleles are as follows: ΔrecA306::Tn10, recB21 recC22, recB268::Tn10, recC266::Tn10, recC73, recD1901::Tn10, recF143, recG258::mini-Tn10 Kan, recJ284::Tn10, recN1502::Tn5, rec01504::Tn5, recQ1803::Tn3, recR252::mini-Tn10 Kan, ΔruvAB100::Cm, ΔruvC100::Cm, ruvC53 eda::Tn10. B: Various recBCD alleles in V66 background. C: In a recBC sbcA background. The mutation alleles are the same as in A except for recE159, recQ1801, recT101::Tn10, and ΔruvAB::Tc. D: In a recBC sbcBC background. The mutation alleles are the same as in A except for recN262 tyrA16::Tn10.