Gce Model Questions Vol1 2018 Biology Question 23

A mixed bacterial population contains \(1.0 \times 10^{8}\) cells. Among them, \(5.0 \times 10^{5}\) are donor cells that carry a plasmid conferring antibiotic resistance. Conjugation occurs when a donor contacts a recipient; the probability of successful plasmid transfer per donor‑recipient contact is \(5 \times 10^{-7}\) per hour. Each donor makes one random contact per hour. Simultaneously, free plasmid DNA is present at a concentration of \(10\) ng ml\(^{-1}\) (≈\(1.5 \times 10^{10}\) copies ml\(^{-1}\)). The probability that a recipient cell takes up a DNA copy per hour is \(2 \times 10^{-8}\). Over a period of 4 h, calculate the expected number of newly resistant cells produced by (i) conjugation and (ii) transformation, and state which mechanism is likely to generate more resistant cells.