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

In the context of microbial drug resistance, the introduction of new genes into a population is necessary for the synthesis of new enzymes that inactivate drugs, which often occurs through horizontal gene transfer using plasmids or transposons.

Step-by-step explanation:

Microbial drug resistance can be caused by mutations or by the introduction of new genes into a population. When considering the options provided, the one that can only be caused by the introduction of new genes into a population is the synthesis of new enzymes that inactivate the drug. This typically involves genes that code for enzymes capable of modifying or degrading the drug substance, such as the production of beta-lactamase enzymes that can break down beta-lactam antibiotics.

Mutations generally lead to other forms of resistance, such as alteration of drug targets (e.g., penicillin-binding proteins) or reduced drug uptake. However, the production of entirely new enzymes to inactivate drugs almost always requires the acquisition of new genetic material through mechanisms like horizontal gene transfer (HGT), often facilitated by plasmids or transposons.