All of the following are transcribed from DNA except

Options

A. exons
B. introns
C. rRNA
D. DNA

Answer

To solve the question "All of the following are transcribed from DNA except," we will analyze each option provided in the question to determine which one is not transcribed from DNA.

### Step-by-Step Solution:

1. **Understanding Transcription**:
- Transcription is the process by which a segment of DNA is copied into RNA by the enzyme RNA polymerase. This process is essential for gene expression.

2. **Analyzing the Options**:
- **Option 1: Exons**:
- Exons are the coding regions of a gene that are transcribed into mRNA. They are part of the RNA transcript that codes for proteins. Therefore, exons are transcribed from DNA.
- **Conclusion**: Exons are transcribed from DNA (Incorrect option).

- **Option 2: Introns**:
- Introns are the non-coding regions of a gene that are also transcribed into the primary RNA transcript but are removed during RNA processing. Hence, introns are also transcribed from DNA.
- **Conclusion**: Introns are transcribed from DNA (Incorrect option).

- **Option 3: rRNA**:
- Ribosomal RNA (rRNA) is a type of RNA that is synthesized from DNA. It is transcribed from ribosomal DNA (rDNA) and is a crucial component of ribosomes. Therefore, rRNA is transcribed from DNA.
- **Conclusion**: rRNA is transcribed from DNA (Incorrect option).

- **Option 4: DNA**:
- DNA itself cannot be transcribed from DNA. The process that involves copying DNA to produce more DNA is called replication, not transcription. Therefore, DNA is not transcribed from DNA.
- **Conclusion**: DNA is not transcribed from DNA (Correct option).

3. **Final Answer**:
- The correct answer is **DNA** because it is not transcribed from DNA.