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.

Cholesterol (koh-LES-ter-ol) is a fat-like substance that has many functions in the body. Cholesterol moves through the body in the blood. The amount of cholesterol in the blood is controlled by proteins, including the PCSK9 protein. The PCSK9 protein is encoded by the PCSK9 gene.
The PCSK9 protein adds cholesterol to the blood. The action of the PCSK9 protein can lead to blood cholesterol levels that may, over time, cause heart disease.
A certain person had a mutation in the PCSK9 gene. Compared to the PCSK9 gene without a mutation, the mutated PCSK9 gene encoded a form of the PCSK9 protein with a different structure.
This different form of the PCSK9 protein could add only a small amount of cholesterol to the blood. So, this person had a lower risk of developing heart disease than a person with more cholesterol in their blood.
Figure: an illustration of cholesterol with red blood cells.
Complete the sentence.
The mutation in the () affected the structure and function of the ().
A. PCSK9 protein . . . PCSK9 gene
B. PCSK9 gene . . . PCSK9 protein
Determine the correct option from the provided choices and reply with its corresponding letter.

B