The linking of antibiotic resistance gene with the plasmid vector became possible with :

Options

A. Exonucleases
B. DNA ligase
C. Endonucleases
D. Lipman

Answer

To answer the question regarding the linking of an antibiotic resistance gene with a plasmid vector, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Components**:
- The question involves a plasmid vector and an antibiotic resistance gene. A plasmid is a small, circular piece of DNA that can replicate independently of chromosomal DNA in bacteria.

2. **Identifying the Process**:
- To link an antibiotic resistance gene to a plasmid, we need to perform a molecular cloning technique. This involves cutting the plasmid and the gene of interest so that they can be joined together.

3. **Role of Enzymes**:
- Various enzymes are involved in this process:
- **Exonucleases**: These enzymes remove nucleotides from the ends of DNA. They are not suitable for linking DNA fragments.
- **Endonucleases**: These enzymes cut DNA at specific internal sites. They are used to create compatible ends for ligation but do not directly link DNA fragments.
- **DNA Ligases**: These enzymes are crucial for joining two DNA fragments together. They catalyze the formation of phosphodiester bonds between the sugar-phosphate backbone of DNA.

4. **Conclusion**:
- The linking of the antibiotic resistance gene with the plasmid vector is accomplished using **DNA ligase**. This enzyme allows the two DNA fragments (the plasmid and the antibiotic resistance gene) to be covalently bonded together, forming a recombinant DNA molecule.

### Final Answer:
The linking of the antibiotic resistance gene with the plasmid vector became possible with **DNA ligases**.

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