Question

Microbial drug resistance can be caused by mutations or by introduction of new genes into a population. Which of the following can only be caused by the introduction of new genes into a population?

1) a metabolic pathway in the bacterium is shut down
2) binding sites for the drug are reduced in number or affinity to the drug
3) new enzymes that inactivate the drug are synthesized
4) uptake of the drug into the bacterium is diminished

Answer 1

New enzymes that inactivate a drug, such as ß-lactamases, are created through the introduction of new genes into a microbial population, usually via horizontal gene transfer, not by mutations.

The correct answer is option: 3) new enzymes that inactivate the drug are synthesized.

Step-by-step explanation:

1) Metabolic pathway shutdown: This can be a result of mutations affecting enzymes involved in a metabolic pathway, which can be caused by mutations or the introduction of new genes.

2) Reduction in binding sites: This can be caused by mutations affecting the structure or number of binding sites on target molecules. Mutations can occur naturally or be induced.

3) Synthesis of new enzymes: This specifically involves the introduction of new genes into a population. Horizontal gene transfer, such as through plasmids or other mobile genetic elements, can bring in genes that encode enzymes capable of inactivating drugs.

4) Diminished drug uptake: This can be caused by mutations affecting transport proteins involved in drug uptake. Mutations can occur naturally or be induced.

So, the only option that is specifically associated with the introduction of new genes is "new enzymes that inactivate the drug are synthesized" (Option 3).