Which of the following methods is involved in identifying all genes that are expressed as RNA?

Options

A. ESTs
B. Sequence annotation
C. Gel electrophoresis
D. RFLP

Answer

To determine which method is involved in identifying all genes that are expressed as RNA, we will analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Question**:
The question asks for a method that identifies all genes expressed as RNA. This means we are looking for a technique that can analyze RNA transcripts from genes.

**Hint**: Focus on methods that specifically deal with RNA rather than DNA.

2. **Analyzing Option A: ESTs (Expressed Sequence Tags)**:
- ESTs are short sequences of DNA that are derived from expressed RNA.
- They are typically about 200 to 300 nucleotides long and represent portions of mRNA.
- Since they are derived from RNA, ESTs are indeed used to identify genes that are actively expressed.

**Hint**: Think about how ESTs relate to RNA and gene expression.

3. **Analyzing Option B: Sequence Annotation**:
- Sequence annotation involves adding descriptive information to DNA sequences.
- This process does not specifically focus on RNA or gene expression but rather on the features of the DNA itself.

**Hint**: Consider whether this method deals with RNA or just DNA features.

4. **Analyzing Option C: Gel Electrophoresis**:
- Gel electrophoresis is a technique used for separating and analyzing macromolecules like DNA and RNA.
- However, it does not identify genes expressed as RNA; it merely separates RNA fragments based on size.

**Hint**: Remember that separation techniques do not identify gene expression directly.

5. **Analyzing Option D: RFLP (Restriction Fragment Length Polymorphism)**:
- RFLP is a method used to analyze the lengths of DNA fragments that are produced by restriction enzymes.
- This method is primarily used for DNA analysis and does not pertain to RNA expression.

**Hint**: Focus on whether this method is related to RNA or just DNA polymorphisms.

6. **Conclusion**:
After analyzing all options, the correct method that identifies all genes expressed as RNA is **Option A: ESTs (Expressed Sequence Tags)**.

### Final Answer:
**The method involved in identifying all genes that are expressed as RNA is ESTs (Expressed Sequence Tags).**