How many of the following is/are correct statement?
(A)In capping an unusual nucleotides is added to the 3' end of hn RNA
(B)In tailing adenylated residues are added at 3' end in a template independent manner.
(C)The untranslated regions (UTR) are required for efficient DNA replication process.
(D)The DNA-dependent DNA polymerases catalyse polymerisation only in one direction that is 5' ` to ` 3'.

Options

A. Four
B. Three
C. Two
D. One

Answer

To solve the question, we need to evaluate each of the four statements provided and determine how many of them are correct.

### Step 1: Evaluate Statement A
**Statement A:** In capping, an unusual nucleotide is added to the 3' end of hnRNA.

- **Analysis:** In eukaryotic cells, the capping process involves the addition of a 7-methylguanylate (m7G) cap to the 5' end of the hnRNA (heterogeneous nuclear RNA), not the 3' end. Therefore, this statement is **false**.

### Step 2: Evaluate Statement B
**Statement B:** In tailing, adenylated residues are added at the 3' end in a template-independent manner.

- **Analysis:** The addition of a poly(A) tail (adenylation) occurs at the 3' end of the pre-mRNA and does not require a template. This statement is **true**.

### Step 3: Evaluate Statement C
**Statement C:** The untranslated regions (UTR) are required for efficient DNA replication process.

- **Analysis:** UTRs are regions of mRNA that are not translated into protein, and they play a role in the regulation of translation and stability of mRNA. They are not required for DNA replication, which occurs in the DNA molecule itself. Thus, this statement is **false**.

### Step 4: Evaluate Statement D
**Statement D:** The DNA-dependent DNA polymerases catalyze polymerization only in one direction that is 5' to 3'.

- **Analysis:** DNA polymerases synthesize new DNA strands by adding nucleotides in the 5' to 3' direction. This statement is **true**.

### Conclusion
Now, we summarize the evaluations:
- Statement A: False
- Statement B: True
- Statement C: False
- Statement D: True

Thus, there are **2 correct statements** (B and D).

### Final Answer
The number of correct statements is **2**.

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