Q20 - Timing Gene Transfer During Bacterial Conjugation

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Linkage, Recombination & Genetic Mapping

In an experiment, two bacterial strains, I and II, were allowed to conjugate. Strain I contained genes allowing it to grow on media lacking arginine and uracil, and with galactose as its sole carbon source, and even in the presence of the antibiotic Kanamycin (+KM). Strain II could not grow on these media. After a certain incubation time, Strain II was grown on selective media until 100 isolated colonies were obtained. The success of conjugation was assessed (Tab.). Table. Success of growth of Strain II in (%) after conjugation.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. The gene marker 'KM resistance' is transferred before the gene required for uracil synthesis

B. The data suggest that a full bacterial genome can be transferred via conjugation in less than 15 minutes

C. The data suggest that a small fraction of recipient colonies can be expected to grow on +KM medium even in the absence of conjugation

D. More than 20% of all colonies incubated for 15 minutes are expected to grow on a medium lacking both arginine and uracil

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Question reproduced from IBO 2015, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)