MDCAT Biology MCQ #3648

In a study of the evolution of antibiotic resistance in bacteria, researchers find that resistance is more likely to develop in bacteria that are exposed to low levels of antibiotics. What is the primary mechanism driving this evolutionary change?

MDCAT Biology MCQ #3648

  1. Question 1

    Q1. In a study of the evolution of antibiotic resistance in bacteria, researchers find that resistance is more likely to develop in bacteria that are exposed to low levels of antibiotics. What is the primary mechanism driving this evolutionary change?

    • A) Horizontal gene transfer from resistant bacteria
    • B) Natural selection acting on pre-existing genetic variation
    • C) Mutation introducing a new resistance gene
    • D) Genetic drift due to the bottleneck effect

    Answer: Natural selection acting on pre-existing genetic variation

    Explanation: Natural selection favors resistant bacteria, most tempting wrong option fails as mutation is less common.