In the process of insertional inactivation
1) a recombinant DNA is inserted within the coding sequence of enzyme β -galactosidase, resulting in inactivation of the enzyme
2) a recombinant DNA is inserted within the coding sequence of proteins involved in the replication of the plasmid
3) a recombinat DNA is inserted within the recongnition site for EcoRl
4) none of these

Options

A. 1) a recombinant DNA is inserted within the coding sequence of enzyme `beta`-galactosidase, resulting in inactivation of the enzyme
B. 2) a recombinant DNA is inserted within the coding sequence of proteins involved in the replication of the plasmid
C. 3) a recombinat DNA is inserted within the recongnition site for EcoRl
D. 4) none of these

Explanation

To solve the question regarding insertional inactivation, we will analyze each option provided and determine which one correctly describes the process.

### Step 1: Understand Insertional Inactivation
Insertional inactivation is a technique used in molecular biology where a foreign DNA fragment is inserted into a specific gene sequence, disrupting its function. This is commonly used in cloning to identify successful recombinant DNA.

### Step 2: Analyze Each Option
1. **Option 1**: A recombinant DNA is inserted within the coding sequence of the enzyme β-galactosidase, resulting in inactivation of the enzyme.
- This statement is true. The insertion of foreign DNA into the LacZ gene (which encodes β-galactosidase) leads to the inactivation of the enzyme, which is a classic example of insertional inactivation.

2. **Option 2**: A recombinant DNA is inserted within the coding sequence of proteins involved in the replication of the plasmid.
- This statement is false. Insertional inactivation specifically refers to the disruption of a gene's function, not the replication proteins.

3. **Option 3**: A recombinant DNA is inserted within the recognition site for EcoRI.
- This statement is misleading. Insertion at a restriction site like EcoRI does not necessarily lead to inactivation of a gene; it is more about the cloning process rather than insertional inactivation.

4. **Option 4**: None of these.
- This option is incorrect because we have already identified that option 1 is correct.

### Step 3: Conclusion
Based on the analysis, the correct answer is **Option 1**: A recombinant DNA is inserted within the coding sequence of the enzyme β-galactosidase, resulting in inactivation of the enzyme.

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