**Core Concept**
The genetic code is a set of rules used by living cells to translate information encoded within genetic material (DNA or RNA sequences) into proteins. This universal code is made up of 64 codons, each specifying one of 20 amino acids or a stop signal.

**Why the Correct Answer is Right**
The genetic code is almost universal, meaning it is shared across different species, but there are some variations. The correct answer will highlight a notable exception to this rule. Understanding the genetic code and its exceptions is crucial for deciphering the relationship between DNA sequences and protein structures.

**Why Each Wrong Option is Incorrect**
**Option A:**
* This option is not a known exception to the genetic code, so it's likely a distractor.

**Option B:**
* This option might be true, but it's not the best choice for an exception to the genetic code. Further clarification is needed to confirm its accuracy.

**Option C:**
* This option is a known exception to the genetic code. In mitochondria, the genetic code is different from the standard code, with some codons specifying different amino acids or stop signals.

**Option D:**
* This option is not a known exception to the genetic code. It might be a distractor or a statement that is true in certain contexts but not relevant to the genetic code.

**Clinical Pearl / High-Yield Fact**
One of the most significant exceptions to the genetic code is found in mitochondria, where the genetic code is different from the standard code. This difference highlights the unique characteristics of mitochondrial DNA and its role in energy production within cells.

**Correct Answer:** C. This option highlights a notable exception to the genetic code, specifically in mitochondria, where the genetic code is different from the standard code.