The efficiency of the cell to take up rDNA is increased by

Options

A. Monovalent cation
B. Divalent cation
C. Monovalent anion
D. Divalent anion

Answer

To solve the question regarding the efficiency of the cell to take up recombinant DNA (rDNA), we will follow these steps:

### Step-by-Step Solution:

1. **Understanding rDNA**:
- Recombinant DNA (rDNA) is formed by combining DNA from different sources. It typically involves inserting foreign DNA into a plasmid, which acts as a vector to carry this DNA into a target cell.

2. **Identifying the Target Cell**:
- The target cell can be any type of cell, such as bacterial cells (like E. coli), plant cells, or animal cells. The goal is to introduce the rDNA into these cells effectively.

3. **Charge of rDNA**:
- rDNA has a negative charge due to the phosphate groups present in the DNA backbone. This negative charge plays a crucial role in how the DNA interacts with the cell membrane.

4. **Role of Cations**:
- To enhance the uptake of rDNA by the target cell, we need to consider the charge interactions. Since rDNA is negatively charged, it will be attracted to positively charged ions (cations).

5. **Types of Cations**:
- The options provided include monovalent cations, divalent cations, monovalent anions, and divalent anions.
- Monovalent cations (like sodium) and divalent cations (like calcium) can both be used to facilitate DNA uptake.

6. **Choosing the Right Cation**:
- Among the cations, divalent cations are often more effective in promoting the uptake of rDNA. Calcium chloride (CaCl2), a divalent cation, is commonly used in laboratory protocols to increase the efficiency of transformation in bacterial cells.

7. **Conclusion**:
- The efficiency of the cell to take up rDNA is increased by the presence of divalent cations, specifically calcium ions. Therefore, the correct answer is **divalent cation**.

### Final Answer:
The efficiency of the cell to take up rDNA is increased by **divalent cation**.

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