Read the following passage carefully and answer the given questions.

Restriction endonuclease on finding its specific recognition sequence, bind to the DNA and cut each of the two strands of the double helix at specific points in their sugar -phosphate backbones. Each restriction endonuclease recognises a specific palindromic nucleotide sequences in the DNA. Since the DNA is enclosed within the membranes, we have to break the cell open to release DNA along with other macromolecules such as RNA, proteins, polysaccharides and also lipids. This can be achieved by treating the bacterial cells/plant or animal tissue with enzymes such as lysozyme (bacteria), cellulase (plant cells), chitinase (fungus). Now a days the most commonly used matrix is agarose which is a natural polymer extracted from sea weeds. The DNA fragments separate (resolve) according to their size through sieving effect provided by the agarose gel. The first restriction endonuclease-Hind II, whose functioning depended on a specific DNA nucleotide sequence was isolated and characterised five years later. It was found that Hind II always cut DNA molecules at a particular point by recognising a specific sequence of six base pairs. In addition to 'ori', the vector requires a selectable marker, which helps in identifying and eliminating non- transformants and selectively permitting the growth of the transformants. Transformation is a procedure through which a piece of DNA is introduced in a host bacterium. Normally, the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers for E. coli.

Transformation is a procedure through which:

A piece of DNA is introduced in a host bacterium

The correct answer is Option (3) – A piece of DNA is introduced in a host bacterium

Transformation is a procedure through which a piece of DNA is introduced in a host bacterium . Bacterial cells are briefly exposed to high temperature, which creates temporary pores in the cell wall. These pores allow the plasmid DNA to enter the bacterial cell, promoting successful transformation. The transient pores close again, and the transformed bacteria can later express the antibiotic resistance gene, allowing them to survive in the presence of antibiotics.]

The heat shock process creates temporary pores in the cell wall by disrupting the structure of the cell wall proteins. These pores are small enough to allow plasmid DNA to enter the cell, but they are too large for the plasmid DNA to exit the cell. Once the plasmid DNA is inside the cell, it can be integrated into the bacterial chromosome and expressed. The heat shock method is a very efficient way to transform bacteria. It is often used in conjunction with other methods, such as calcium chloride treatment, to increase the transformation efficiency.