Which one of the following is not a correct combination of enzyme and organism used for breaking the cells?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Ligase - animal cells
To isolate DNA, the cell must first be broken open so that the DNA comes out. Each kind of cell has a different outer covering, so a different enzyme is used to break it: lysozyme for bacteria, cellulase for plant cells and chitinase for fungi.
(1) Lysozyme - bacteria — A correct combination. Lysozyme breaks down the bacterial cell wall.
(2) Cellulase - plant cells — A correct combination. The plant cell wall is made of cellulose, which cellulase breaks down.
(3) Chitinase - fungus — A correct combination. The fungal cell wall is made of chitin, which chitinase breaks down.
(4) Ligase - animal cells — Not a correct combination. DNA ligase does not break anything. It joins pieces of DNA, for example a gene into a vector. Animal cells have no cell wall, so no wall-digesting enzyme is needed for them.
NCERT Extract:
Isolation of the Genetic Material (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).”