The term 'recombinant DNA' refers to

Options

A. DNA of the host cell
B. DNA with a piece of foreign DNA
C. DNA with selectable marker
D. DNA with more than one recognition sites

Explanation

To answer the question "The term 'recombinant DNA' refers to," we need to analyze the options provided and understand the concept of recombinant DNA.

### Step-by-Step Solution:

1. **Understanding Recombinant DNA**:
- Recombinant DNA is a form of DNA that is created by combining genetic material from two different sources. This process involves taking a piece of DNA from one organism and inserting it into the DNA of another organism.

2. **Analyzing the Options**:
- **Option A: DNA of the host cells**: This option refers to the DNA that is naturally present in the host organism. It does not involve any foreign DNA and thus is not correct.
- **Option B: DNA with a piece of foreign DNA**: This option accurately describes recombinant DNA. It involves the combination of the host DNA with a piece of DNA that is foreign to it, which is the essence of recombinant DNA technology.
- **Option C: DNA with selectable marker**: Selectable markers are used in genetic engineering to identify cells that have taken up the recombinant DNA, but they are not a defining feature of recombinant DNA itself. Therefore, this option is incorrect.
- **Option D: DNA with more than one recognition site**: Recognition sites are specific sequences where restriction enzymes cut DNA. While recombinant DNA can involve multiple recognition sites, this option does not define recombinant DNA. Hence, it is also incorrect.

3. **Conclusion**:
- Based on the analysis, the correct answer is **Option B: DNA with a piece of foreign DNA**. This is the definition of recombinant DNA, as it involves the integration of foreign genetic material into the DNA of another organism.

### Final Answer:
The term 'recombinant DNA' refers to **DNA with a piece of foreign DNA**.

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