## Core Concept
The gene responsible for coding plasma cholinesterase, also known as butyrylcholinesterase (BChE), is located on a specific chromosome. Plasma cholinesterase is an enzyme that plays a crucial role in the metabolism of certain drugs, such as succinylcholine and ester local anesthetics.

## Why the Correct Answer is Right
The correct answer, , indicates that the gene coding for plasma cholinesterase is located on chromosome 3. This enzyme is synthesized in the liver and secreted into the bloodstream, where it hydrolyzes choline esters. The BChE gene is indeed situated on chromosome 3, specifically at position q26.

## Why Each Wrong Option is Incorrect
* **Option A:** - This option is incorrect because chromosome 1 does not carry the gene for plasma cholinesterase.
* **Option B:** - This option is incorrect because chromosome 2 is not associated with the coding of plasma cholinesterase.
* **Option D:** - This option is incorrect because chromosome 4 does not harbor the gene responsible for plasma cholinesterase.

## Clinical Pearl / High-Yield Fact
A notable clinical correlation is that genetic variations in the BChE gene can lead to abnormal enzyme activity, affecting the metabolism of certain drugs. For instance, individuals with atypical BChE may experience prolonged apnea after receiving succinylcholine due to decreased enzyme activity.

## Correct Answer Line
**Correct Answer: C. **