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 identify all genes that are expressed as RNA, we need to analyze the provided options and determine which method is specifically designed for this purpose.

### Step-by-Step Solution:

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

2. **Evaluating the Options**:
- **Option 1: ESTs (Expressed Sequence Tags)**: ESTs are short sequences derived from the expressed mRNA. They are used to identify gene transcripts and can help in mapping the genes that are actively expressed. This makes ESTs a suitable method for identifying genes expressed as RNA.

- **Option 2: Sequence Annotation**: This process involves adding information to a sequence, such as identifying features of genes, but it does not specifically identify all expressed genes as RNA. It is more about interpreting the sequence rather than identifying expressed genes.

- **Option 3: Gel Electrophoresis**: This technique separates nucleic acids based on size but does not specifically identify genes expressed as RNA. It is used for analyzing the size of RNA or DNA fragments rather than identifying all expressed genes.

- **Option 4: RFLP (Restriction Fragment Length Polymorphism)**: RFLP is a technique used to analyze the length of DNA fragments after restriction enzyme digestion. It is not directly related to identifying expressed RNA genes.

3. **Conclusion**: Among the options provided, ESTs (Expressed Sequence Tags) are the most relevant method for identifying all genes that are expressed as RNA. Therefore, the correct answer is **Option 1: ESTs**.