Question

Significance of 'heat shock' method in bacterial transformation is to facilitate:

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

Answer 1

The correct option is C Uptake of DNA through transient pores in the bacterial cell wall

Competent cells:

Cells which have the ability to uptake the foreign DNA such as recombinant DNA are called competent cells.

Heat shock method:

Heat shock method is one of the most common methods of making bacterial competent cells.

● In this method, bacterial cells are treated with divalent ions such as calcium and magnesium ions which cause the condensation or shrinkage of DNA molecules and the positive charge of these divalent molecules facilitates the crossing of the negatively charged cell membrane.

● A heat shock is provided for a brief time period which creates transient pores within the bacterial cell membrane.

● These pores allow the DNA of interest to enter into the bacteria.

● These pores are closed by putting the cells back on ice. The low temperature of the ice seals the pores.

Final answer:

c. Uptake of DNA through transient pores in the bacterial cell wall