Question

You prepared three plates with a bacterium containing an unknown plasmid. One plate contained ampicillin, one plate contained tetracycline, and one plate was exposed to UV light. After incubating the plates at 37°C for 24 hours, you observed bacterial colonies on the plate containing ampicillin and on the plate exposed to UV light, but not on the plate containing tetracycline. Which of the following genes was not in the unknown plasmid?

a.ampicillin resistance
b.tetracycline resistance
c.UV resistance
d.All genes were in the unknown plasmid.

Answer 1

The unknown plasmid contains the ampicillin resistance gene but not the tetracycline resistance gene, as evidenced by bacterial colony growth on the ampicillin plate and no growth on the tetracycline plate. The presence of colonies after UV exposure suggests either an inherent tolerance or insufficient UV dosage.

Step-by-step explanation:

When examining the growth of E. coli bacteria on plates containing different antibiotics, the presence or absence of bacterial colonies can indicate the resistance conferred by plasmids carried by the bacteria. If bacterial colonies were present on the ampicillin plate but not on the tetracycline plate, this suggests that the unknown plasmid contains the ampicillin resistance gene but not the tetracycline resistance gene. Since there were colonies on the plate exposed to UV light, we can infer that the plasmid doesn't contain a UV resistance gene, but the bacteria may have an inherent tolerance to UV or the dosage and time of exposure were not sufficient to prevent growth.