During heat shock to the bacterium, the temperature used for giving thermal shock is :

Options

A. `82^(@)`C
B. `100^(@)` C
C. liquid nitrogen
D. `42^(@)` C

Answer

**Step-by-Step Solution:**

1. **Understanding Heat Shock**: Heat shock is a technique used to make bacterial cells competent, meaning that they can take up foreign DNA, such as recombinant DNA (rDNA).

2. **Reason for Competence**: Bacterial cells normally cannot take up DNA because DNA is hydrophilic and cannot easily cross the hydrophobic cell membrane. Therefore, we need to modify the bacterial cells to allow DNA uptake.

3. **Process of Heat Shock**: The process involves two main temperature changes:
- First, the bacterial cells are placed on ice. This step helps stabilize the cells and prepares them for the next phase.
- Then, the cells are subjected to a brief heat shock at a temperature of 42 degrees Celsius. This sudden increase in temperature creates a thermal imbalance that makes the cell membrane more permeable to DNA.

4. **Final Step**: After the heat shock, the cells are returned to ice. This helps to stabilize the cells again and allows them to take up the recombinant DNA that has been introduced.

5. **Conclusion**: The specific temperature used for the heat shock process is 42 degrees Celsius.

**Final Answer**: The temperature used for giving thermal shock to the bacterium is 42 degrees Celsius.

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