The episome in an Hfr strain is inserted near the trp (tryptophan operon) locus. This Hfr strain is grown with an F- Trp- strain. From this mating, we isolate an F+ Trp+ strain that can readily impart the Trp+ phenotype to F- Trp- strains, but no other traits are ever transferred. (When the original Hfr strain is mated with F? strains, traits other than Trp+ can be transferred, although at lower frequency than Trp+.) What most likely has happened?
