In t-RNA

Options

A. CCA - OH is present at 5-end
B. `TPsiC` loop for attaching the amino acids
C. DHU loop for binding with AA-activating enzyme
D. There are three recognition sites

Answer

To answer the question regarding tRNA (transfer RNA), we will analyze the statements provided and determine their correctness step by step.

### Step-by-Step Solution:

1. **Understanding the Structure of tRNA**:
- tRNA is a small RNA molecule that plays a crucial role in protein synthesis by bringing amino acids to the ribosome.
- It has a cloverleaf structure with several important regions: the acceptor stem, the D loop, the T loop, and the anticodon loop.

2. **Evaluating the First Statement**:
- The statement claims that "CCA OH is present at the 5 prime end."
- **Correction**: The CCA sequence is actually located at the 3' end of tRNA, not the 5' end. Therefore, this statement is **incorrect**.

3. **Evaluating the Second Statement**:
- The statement claims that "T5C loop is for attaching the amino acids."
- **Correction**: The T5C loop (or T loop) is primarily involved in binding to the ribosome during protein synthesis, not for attaching amino acids. Thus, this statement is also **incorrect**.

4. **Evaluating the Third Statement**:
- The statement claims that "D loop is for the binding with the activating enzyme."
- **Correction**: The D loop (or DHU loop) does indeed play a role in binding to the aminoacyl-tRNA synthetase, which activates the amino acids. Therefore, this statement is **correct**.

5. **Evaluating the Fourth Statement**:
- The statement claims that "there are three recognition sites."
- **Correction**: In reality, tRNA has four recognition sites: the CCA end, the D loop, the T loop, and the anticodon loop. Therefore, this statement is **incorrect**.

### Conclusion:
Based on the evaluation of the statements:
- The only correct statement is the third one regarding the D loop's function.
- Thus, the correct answer is **option 3 only**.