Which type of ion use to increase the efficiency uptake of DNA by bacterial cell ?

Answer

**Step-by-Step Solution:**

1. **Understanding Competent Cells**: The question asks about the type of ion that increases the efficiency of DNA uptake by bacterial cells. To answer this, we first need to understand what a competent cell is. Competent cells are bacterial cells that have been treated to allow them to take up foreign DNA more efficiently.

2. **Identifying the Ion**: The specific type of ion used to enhance the uptake of DNA by bacterial cells is a divalent ion. Divalent ions have a charge of +2 and can interact effectively with both the DNA and the bacterial cell membrane.

3. **Calcium Ion**: The most commonly used divalent ion for making bacterial cells competent is the calcium ion (Ca²⁺). It is typically used in the form of calcium chloride (CaCl₂).

4. **Mechanism of Action**: Calcium ions help to mask the negative charges on both the DNA and the bacterial cell membrane. This masking reduces the electrostatic repulsion between the negatively charged DNA and the negatively charged bacterial cell membrane, facilitating the uptake of DNA.

5. **Heat Shock Treatment**: After treating the bacterial cells with calcium chloride, a heat shock treatment is applied. This involves exposing the cells to a brief period of heat followed by a rapid cooling. This process creates pores in the bacterial membrane, further increasing its permeability to DNA.

6. **Conclusion**: Therefore, the type of ion used to increase the efficiency of DNA uptake by bacterial cells is the divalent ion, specifically calcium ions in the form of calcium chloride.

**Final Answer**: Divalent ions, specifically calcium ions (Ca²⁺) in the form of calcium chloride (CaCl₂), are used to increase the efficiency of DNA uptake by bacterial cells.

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