Question:
Significance of heat shock method in bacterial transformation is to facilitate which one of the following steps ?
Significance of heat shock method in bacterial transformation is to facilitate which one of the following steps ?
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Heat shock briefly opens pores in the cell wall so that the recombinant DNA can enter.
Updated On: Oct 23, 2026
- Binding DNA to the cell wall
- Uptake of DNA through membrane transport proteins
- Uptake of DNA through transient pores in the bacterial cell wall
- Expression of antibiotic resistance genes
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The Correct Option is C
Solution and Explanation
Step 1: Recall the method:
Bacterial cells are treated with a divalent cation such as calcium, so that they become competent. They are incubated with the recombinant DNA on ice.
Step 2: The heat shock step:
The cells are then placed briefly at 42 degrees Celsius (heat shock) and put back on ice. This makes the DNA enter the cell.
Step 3: Why the DNA enters:
The sudden temperature change opens transient pores in the cell wall. The DNA slips in through these pores. So (C) is right.
Step 4: Check the other options:
DNA is not carried across by membrane transport proteins, so (B) is wrong. Heat shock is not about binding to the wall, so (A) is wrong. Expression of resistance genes happens later, after DNA is inside, so (D) is wrong.
Final Answer:
The correct option is (C).
Bacterial cells are treated with a divalent cation such as calcium, so that they become competent. They are incubated with the recombinant DNA on ice.
Step 2: The heat shock step:
The cells are then placed briefly at 42 degrees Celsius (heat shock) and put back on ice. This makes the DNA enter the cell.
Step 3: Why the DNA enters:
The sudden temperature change opens transient pores in the cell wall. The DNA slips in through these pores. So (C) is right.
Step 4: Check the other options:
DNA is not carried across by membrane transport proteins, so (B) is wrong. Heat shock is not about binding to the wall, so (A) is wrong. Expression of resistance genes happens later, after DNA is inside, so (D) is wrong.
Final Answer:
The correct option is (C).
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