The type of RNA that characteristically contains methylated purines and pyrimidines is :

Options

A. tRNA
B. mRNA
C. rRNA
D. All of above

Answer

To solve the question, "The type of RNA that characteristically contains methylated purines and pyrimidines is:", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of RNA**:
- RNA is made up of nitrogenous bases, which include purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil).

2. **Identify Methylation**:
- Methylation refers to the addition of a methyl group (CH3) to the nitrogenous bases. This process can occur in various types of RNA.

3. **Different Types of RNA**:
- The main types of RNA are:
- mRNA (messenger RNA)
- tRNA (transfer RNA)
- rRNA (ribosomal RNA)

4. **Focus on mRNA**:
- During the synthesis of mRNA, a process called capping occurs at the 5' end of the RNA. This involves the addition of a methylated guanosine cap (methyl guanosine triphosphate).
- Additionally, the 3' end of mRNA undergoes tailing, where a poly-A tail (a series of adenine bases) is added.

5. **Conclusion**:
- Since the question specifically asks for the type of RNA that contains methylated purines and pyrimidines, and given that mRNA undergoes methylation during its processing, the correct answer is **mRNA**.

### Final Answer:
The type of RNA that characteristically contains methylated purines and pyrimidines is **mRNA (messenger RNA)**.

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