Structure involved in genetic engineering is

Options

A. (a) Plastid
B. (b) Restriction endonuclease
C. (c) DNA polymerase I
D. (d) Prochromosome

Answer

### Step-by-Step Solution:

1. **Understanding Genetic Engineering**: Genetic engineering is a technology that involves altering the genetic makeup of organisms. This is primarily done through the production of recombinant DNA.

2. **Recombinant DNA Technology**: This technology allows for the combination of DNA from different sources. The goal is to modify the genes of an organism to achieve desired traits, such as disease resistance in plants or rectifying genetic disorders in humans.

3. **Key Components of Genetic Engineering**:
- **Desired DNA Sequence**: This is the specific DNA segment that needs to be altered or inserted.
- **Restriction Endonucleases**: These are enzymes that act as molecular scissors. They cut DNA at specific sites, allowing for the insertion or removal of DNA segments.
- **DNA Ligases**: These enzymes act as molecular glue. They join the cut DNA strands together to form recombinant DNA.

4. **Process of Creating Recombinant DNA**:
- Identify the target DNA sequence that needs alteration.
- Use restriction endonucleases to cut the DNA at specific locations.
- Insert the desired DNA sequence.
- Use DNA ligases to join the original DNA with the new DNA, resulting in recombinant DNA.

5. **Evaluating the Options**:
- **A. Plastid**: Incorrect. Plastids are organelles in plant cells involved in food synthesis and storage.
- **B. Restriction Endonucleases**: Correct. These are essential for cutting DNA at specific sites during genetic engineering.
- **C. DNA Polymerase I**: Incorrect. This enzyme is involved in DNA repair and synthesis, not directly in genetic engineering.
- **D. Prochromosome**: Incorrect. This term refers to the nucleoid in prokaryotes, not a structure involved in genetic engineering.

6. **Conclusion**: The structure involved in genetic engineering is **B. Restriction Endonucleases**.