In an Hfr (high-frequency recombination) strain, the F plasmid is integrated into the bacterial chromosome. Conjugation begins when relaxase nicks the DNA at oriT inside the integrated F factor, and a single strand of the chromosome is fed 5′-end-first through the mating-pair pilus/channel into the recipient, while rolling-circle replication resynthesizes the complementary strand behind it in the donor:
Transfer length: L(t) = v · t (constant-velocity model)
Q10 rate law: v(T) = v(37°C) · Q10^((T-37)/10), Q10 ≈ 2
Full E. coli chromosome ≈ 100 map-minutes at 37 °C ≈ 4.6 Mbp
Because the mating bridge is mechanically fragile, it almost always breaks before the entire ~100-minute chromosome transfers — so only the genes nearest oriT reliably cross. This is exactly the phenomenon Wollman and Jacob exploited in the 1950s interrupted-mating experiment: shear the mating pairs apart (originally in a kitchen blender) at a chosen time, then assay the recipient for which donor markers arrived. Because transfer proceeds at an almost constant rate and always in the same order for a given Hfr strain, the "time of entry" of each marker is a direct linear measure of its position on the chromosome — this is how the first genetic maps of E. coli were built, in minutes rather than base pairs.
- Transfer rate — how fast simulated chromosome-minutes elapse per real second (a visualization speed-up, not the literal transfer speed).
- Temperature — conjugation is enzymatic and temperature-dependent; the effective rate is scaled by a Q10 ≈ 2 factor around the 37 °C optimum, and falls toward zero as temperature drops far below it.
- Interrupt Mating — mimics the blender step: freezes transfer instantly, locking in whichever markers already crossed the bridge.
- Marker entry times shown are representative of a classic HfrH-style map (thr, leu, azi, ton, lac, gal, trp) — real values are strain- and map-orientation-dependent.