An antibiotic resistant gene in a vector usually helps in the selection of

Options

A. a) competent cells
B. b) transformed cells
C. c) recombinant cells
D. d)none of the above

Explanation

To solve the question regarding the role of an antibiotic resistant gene in a vector, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Context**:
- The question asks about the function of an antibiotic resistant gene in a vector. Vectors are used in biotechnology to transfer foreign DNA into host cells.

2. **Identifying Competent Cells**:
- Competent cells are those that can take up foreign DNA. However, the presence of an antibiotic resistant gene does not help in identifying competent cells. Thus, this option is incorrect.

3. **Identifying Transformed Cells**:
- Transformed cells are those that have successfully taken up the foreign DNA, including the antibiotic resistance gene. These cells can survive and grow in an antibiotic-containing medium because they possess the resistance gene. Therefore, this option is correct.

4. **Identifying Recombinant Cells**:
- Recombinant cells contain both the vector DNA and the foreign DNA. The antibiotic resistance gene does not specifically help in identifying these cells, as it does not indicate whether the foreign DNA has been integrated. Hence, this option is incorrect.

5. **Evaluating the "None of the Above" Option**:
- Since we have identified transformed cells as the correct answer, the option "none of the above" is also incorrect.

6. **Conclusion**:
- The correct answer is that an antibiotic resistant gene in a vector usually helps in the selection of **transformed cells**.

### Final Answer:
The correct option is **B) transformed cells**.

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