During isolation of DNA, which enzyme is used to break open bacterial…

The correct answer is Option (3) → Lysozyme

DNA is enclosed within membranes, so the cell must be broken open to release it. The enzyme chosen depends on the kind of cell: lysozyme for bacteria, cellulase for plant cells and chitinase for fungi. Each one breaks down the main material of that cell's wall.

Option (1) Chitinase — Incorrect. Chitinase digests chitin and is used to open fungal cells.

Option (2) Cellulase — Incorrect. Cellulase digests cellulose and is used to open plant cells.

Option (3) Lysozyme — Correct. Lysozyme is the enzyme used to break open bacterial cells and release their DNA.

Option (4) Lipase — Incorrect. Lipase digests fats. It is not one of the enzymes the book lists for breaking cells open during DNA isolation.

NCERT Extract:
Isolation of the Genetic Material (DNA) – “… In order to cut the DNA with restriction enzymes, it needs to be in pure form, free from other macro-molecules. 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).”