Context: The following passage describes the effects of a gene mutation, which is a permanent change in a gene. Read the passage and then follow the instructions below.

Antibiotics are substances that get inside bacterial cells and cause them to die. Doctors often use antibiotics to kill bacteria that cause infections, such as Salmonella typhimurium (S. typhimurium).
A doctor found  that were not killed by certain antibiotics. These bacteria had a mutation in the AcrB gene. The AcrB gene encodes the AcrB protein. The AcrB protein is part of a structure that pumps substances out of the bacterial cell.
Compared to the AcrB gene without a mutation, the mutated AcrB gene encoded a form of the AcrB protein with a different structure.
This different form of the AcrB protein was able to pump certain antibiotics out of the cell.
Figure: S. typhimurium bacteria.
Complete the sentence.
The mutation in the () affected the structure and function of the ().
A. AcrB gene . . . AcrB protein
B. AcrB protein . . . AcrB gene
From the given choices, choose the correct answer and respond with the letter of that choice.

A