In r-DNA technology or genetic engineering elution means-

Options

A. Remove the DNA from centrifuge tube after centrifugation
B. The separated band of DNA are cut out from the gel and extracted from the gel piece
C. Separation of the recombinant protein from recombinant cell
D. Insertion of recombinant DNA into host cell

Answer

**Step-by-Step Solution:**

1. **Understanding r-DNA Technology:**
- r-DNA (recombinant DNA) technology involves manipulating DNA to create new genetic combinations. This process often includes cutting DNA with restriction enzymes and inserting it into vectors for cloning.

2. **Role of Gel Electrophoresis:**
- After DNA is cut into fragments by restriction enzymes, these fragments need to be separated for further analysis or manipulation. Gel electrophoresis is a common technique used for this purpose.

3. **Process of Gel Electrophoresis:**
- In gel electrophoresis, a gel (usually made of agarose) is prepared, and an electric current is applied. The DNA fragments are loaded into wells in the gel. Since DNA is negatively charged, it moves towards the positive electrode when the current is applied.

4. **Separation of DNA Fragments:**
- As the DNA fragments move through the gel, they separate based on size; smaller fragments travel faster and farther than larger ones. This results in distinct bands of DNA.

5. **Elution Process:**
- Elution refers to the process of extracting the separated DNA bands from the gel. This involves cutting out the gel piece containing the desired DNA fragment and then using a solution to extract the DNA from the gel matrix.

6. **Identifying the Correct Answer:**
- In the context of the question, elution specifically means the extraction of the separated DNA from the gel piece after electrophoresis. Therefore, the correct answer is that elution is the process of cutting out the separated bands of DNA from the gel and extracting them.

**Final Answer:**
In r-DNA technology, elution means cutting out the separated bands of DNA from the gel and extracting them for further use.

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