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

Options

A. competent cells
B. transformed cells
C. recombinant cells
D. none of the above

Explanation

**Step-by-Step Solution:**

1. **Understanding the Role of Antibiotic Resistant Genes:**
- Antibiotic resistant genes are often included in vectors (like plasmids) used in genetic engineering. These genes allow for the selection of cells that have successfully taken up the vector.

2. **Identifying the Options:**
- The question provides four options:
a) Competent cells
b) Transformed cells
c) Recombinant cells
d) None of the above

3. **Analyzing Each Option:**
- **Competent Cells:** These are cells that are capable of taking up foreign DNA. They are not selected by antibiotic resistance; rather, they are prepared to undergo transformation. Thus, this option is incorrect.
- **Transformed Cells:** These are cells that have successfully incorporated the foreign DNA (the vector with the antibiotic resistance gene). The presence of the antibiotic resistance gene allows for the selection of these cells when they are grown in the presence of the antibiotic. This option is correct.
- **Recombinant Cells:** These cells contain both the host DNA and the foreign DNA. While the antibiotic resistance gene is part of the vector used to create recombinant DNA, it does not directly help in selecting recombinant cells. This option is incorrect.
- **None of the Above:** Since option B is correct, this option is also incorrect.

4. **Conclusion:**
- The antibiotic resistant gene in a vector primarily helps in the selection of **transformed cells**. Therefore, the correct answer is option **B**.