Ligase enzymes are used in gentic engineering to :

Options

A. Cut open plasmid DNA
B. Insert plasmides into bacteria
C. Isolate the DNA making up a human gene
D. Join human DNA to plasmid DNA

Answer

To solve the question regarding the role of ligase enzymes in genetic engineering, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of Ligase Enzymes**:
- Ligase enzymes are crucial in the process of DNA manipulation. They catalyze the formation of phosphodiester bonds between DNA strands, which is essential for joining DNA fragments together.

2. **Identify the Context of Genetic Engineering**:
- In genetic engineering, ligase enzymes are primarily used in processes such as gene cloning, where segments of DNA need to be joined to form recombinant DNA.

3. **Evaluate the Options Provided**:
- **Option 1**: Cut open plasmid DNA - This is incorrect because cutting DNA is typically done by restriction enzymes, not ligases.
- **Option 2**: Insert plasmids into bacteria - This is also incorrect; ligase does not insert plasmids into bacteria.
- **Option 3**: Isolate the DNA making up a human gene - This is incorrect as well; isolation does not involve ligase.
- **Option 4**: Join human DNA and plasmid DNA - This is correct. Ligase enzymes are indeed used to join these two types of DNA to create recombinant DNA.

4. **Select the Correct Answer**:
- Based on the evaluation, the correct answer is **Option 4: Join human DNA and plasmid DNA**. This is the primary function of ligase enzymes in the context of genetic engineering.

### Final Answer:
Ligase enzymes are used in genetic engineering to **join human DNA and plasmid DNA**.

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