The linking of alien DNA to plasmid vector is possible with the help of :

Options

A. Taq polymerase
B. DNA ligase
C. polyethylene glycol
D. restriction endonuclease type II

Answer

To answer the question, "The linking of alien DNA to plasmid vector is possible with the help of:", we need to analyze the options provided and understand the role of each component in biotechnology.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the method or enzyme that facilitates the linking of foreign (alien) DNA to a plasmid vector. Plasmids are circular DNA molecules used in genetic engineering to clone or express genes.

2. **Evaluating the Options**:
- **Option 1: Taq Polymerase**: This enzyme is primarily used in the Polymerase Chain Reaction (PCR) to amplify DNA. It does not play a role in linking DNA to plasmids.
- **Option 2: DNA Ligase**: This enzyme is crucial for joining two DNA fragments together. It catalyzes the formation of phosphodiester bonds between the DNA backbone, making it the correct answer for linking alien DNA to plasmids.
- **Option 3: Polyethylene Glycol (PEG)**: PEG is used to facilitate the transformation of cells and can help in the uptake of DNA, but it does not directly link DNA to plasmids.
- **Option 4: Restriction Endonuclease Type 2**: These enzymes cut DNA at specific sequences, which is essential for preparing the DNA fragments for ligation but does not itself link the DNA to the plasmid.

3. **Conclusion**: Based on the analysis, the correct answer is **DNA Ligase**, as it is the enzyme that facilitates the joining of alien DNA to plasmid vectors.

### Final Answer:
The linking of alien DNA to plasmid vector is possible with the help of **DNA Ligase**.