F factor excision from Hfr integration

(a) Normal excision (left) restores an Hfr to an F+, whereas aberrant excision (right) forms an F plasmid in an F donor cell. (b) F× F− conjugation produces an exconjugant that is a partial diploid lac+/lac−(a) Normal excision (left) restores an Hfr to an F+, whereas aberrant excision (right) forms an F plasmid in an F donor cell. (b) F× F− conjugation produces an exconjugant that is a partial diploid lac+/lac−

(a) Hfr chromosome oriT Bacterial F factor chromosome lac Normal :xcision Aberran: excision the bacterial DNA loops out during excision. Bacterial F' plasmid Bacterial F‘ plasmid chromosome chromosome The F' factor contains the donor Iac‘ in addition to a full set of F factor genes. (b) F’ cell F‘ cell Bacterial F' factor Bacterial chromosome chromosome Grows on a lactose medium [Unable to grow on N a lactose medium ,J F' cell Conjugation F‘ cell Transfer complete F' cell 1 F‘ exconjugant ability to grow on a lactose medium. Because F’ plasmid transfer The exconjugant is a Iac'llaC' partial diploid and has acquired the was complete. the exconjugant can act as an F' donor.