Which types of nitrogen bases are present in loops to t-RNA ?

Options

A. Only unusual nitrogen bases
B. Only usual nitrogen bases
C. Both usual and unusual nitrogen bases
D. None of the above

Answer

To answer the question about the types of nitrogen bases present in the loops of transfer RNA (tRNA), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of tRNA**:
- tRNA is a type of RNA that has a specific three-dimensional structure, which includes several loops and arms. The main loops in tRNA are the D loop, the anticodon loop, and the T loop.

2. **Identify the Types of Nitrogen Bases**:
- The nitrogen bases in RNA include adenine (A), guanine (G), cytosine (C), and uracil (U). These are considered the "usual" nitrogen bases found in RNA.

3. **Recognize the Presence of Unusual Bases**:
- In addition to the usual nitrogen bases, tRNA also contains "unusual" nitrogen bases. These include modified bases such as ribouridine and pseudouridine, which are derivatives of uracil.

4. **Conclusion**:
- Since tRNA contains both the usual nitrogen bases (A, G, C, U) and unusual nitrogen bases (like ribouridine and pseudouridine), the correct answer to the question is that both types of nitrogen bases are present in the loops of tRNA.

5. **Final Answer**:
- The correct option is **both usual and unusual nitrogenous bases**.