Consider the following statements and identify the correct statements .
I. While using genes encoding antibiotic resistance as selectable markers, such genes are selected for which hots in naturally resistance .
II. Restriction site of Pvull is present in a `"amp"^(2)` gene .
III. Ti plasmid is most widely used in gene transfere in all palnts .
IV. Retrovirues are directly used (unchanged ) to deliver desirable genes into animal cells .

Options

A. All expect I
B. All except III
C. II alone
D. All are incorrect

Answer

To solve the question, we need to evaluate each statement provided and determine whether it is correct or incorrect.

### Step-by-Step Solution:

1. **Statement I: While using genes encoding antibiotic resistance as selectable markers, such genes are selected for which host is naturally resistant.**
- **Evaluation:** This statement is incorrect. Antibiotic resistance genes are used as selectable markers to identify successfully transformed cells. The host cells are typically not naturally resistant; rather, they are made resistant through the introduction of these genes.

2. **Statement II: Restriction site of Pvull is present in an "amp"^(2) gene.**
- **Evaluation:** This statement is also incorrect. The "amp"^(2) gene, which encodes for ampicillin resistance, does not have a restriction site for the enzyme PvuII. PvuII is known to cut at specific sites that are not present in the "amp"^(2) gene.

3. **Statement III: Ti plasmid is most widely used in gene transfer in all plants.**
- **Evaluation:** This statement is incorrect. While the Ti plasmid from Agrobacterium tumefaciens is widely used for gene transfer in many dicotyledonous plants, it is not universally applicable to all plants, especially monocots.

4. **Statement IV: Retroviruses are directly used (unchanged) to deliver desirable genes into animal cells.**
- **Evaluation:** This statement is incorrect. Retroviruses are modified (disarmed) before being used to deliver genes into animal cells. They cannot be used unchanged due to safety and efficacy concerns.

### Conclusion:
All four statements are incorrect.

### Final Answer:
All statements (I, II, III, IV) are incorrect.

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