Practice question

F plasmid, or fertility factor, is 100 kb conjugative plasmid carrying tra operon encoding sex pili, type IV secretion system, and regulation of cell contact. Cells harboring F express F pili, act as donors F+ and initiate conjugation by transferring single-stranded copy of plasmid to F- recipient via pilus. F also integrates rarely to form Hfr. Its role is horizontal transmission of itself and mobilization of other DNAs, spreading genes like antibiotic resistance. Classic Lederberg-Tatum experiments used F to demonstrate bacterial recombination, revolutionizing prokaryotic genetics analysis.