Significance of treating bacterial cells with calcium chloride before transformation is to facilitate

Options

A. Binding to DNA to the cell surface
B. Uptake of DNA through membrane transport proteins
C. Uptake of DNA by creating transient pores in the bacterial cell wall
D. Expression of antibiotic resistance gene

Answer

### Step-by-Step Solution:

1. **Understanding Transformation**: Transformation is the process by which bacterial cells take up foreign DNA from their environment. This is crucial in biotechnology for introducing new genetic material into bacteria.

2. **Role of Calcium Chloride**: Calcium chloride (CaCl2) is commonly used to treat bacterial cells to make them competent for transformation. The calcium ions (Ca²⁺) play a significant role in this process.

3. **Making Cells Competent**: The treatment with calcium chloride increases the permeability of the bacterial cell membrane. This is important because DNA is a hydrophilic molecule and cannot easily cross the hydrophobic lipid bilayer of the cell membrane.

4. **Mechanism of Action**: The calcium ions interact with the negatively charged components of the cell membrane and help create transient pores in the cell wall. This allows the foreign DNA to enter the bacterial cell more efficiently.

5. **Heat Shock Method**: After treating the cells with calcium chloride, the bacterial cells are incubated with the plasmid DNA on ice. Then, they are subjected to a brief heat shock at 42 degrees Celsius, which further facilitates the uptake of DNA by creating a thermal imbalance that encourages DNA entry.

6. **Final Step**: After the heat shock, the cells are returned to ice to stabilize the membrane and allow the DNA to integrate or remain within the cell.

7. **Conclusion**: The significance of treating bacterial cells with calcium chloride before transformation is primarily to facilitate the uptake of DNA by creating transient pores in the bacterial cell wall.

### Answer:
The significance of treating bacterial cells with calcium chloride before transformation is to facilitate the uptake of DNA by creating transient pores in the bacterial cell wall.

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