Read the Passage carefully and answer the questions.
There are two kinds of nucleases - exonucleases and endonucleases. Exonucleases remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA. The cutting of DNA by restriction endonucleases results in the fragments of DNA. These fragments can be separated by a technique known as gel electrophoresis. Since DNA fragments are negatively charged molecules they can be separated by forcing them to move towards the anode under an electric field through a medium/matrix. Small volume cultures cannot yield appreciable quantities of products. To produce in large quantities, the development of bioreactors, where large volumes (100-1000 litres) of culture can be processed, was required. Thus, bioreactors can be thought of as vessels in which raw materials are biologically converted into specific products, individual enzymes, etc., using microbial plant, animal or human cells. PCR stands for Polymerase Chain Reaction. In this reaction, multiple copies of the gene (or DNA) of interest are synthesised in vitro using two sets of primers (small chemically synthesised oligonucleotides that are complementary to the regions of DNA) and the enzyme DNA polymerase.
Identify the correct enzyme to release the DNA from the fungal cells?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Chitinase
DNA lies inside the cell, within membranes and, in many cells, a cell wall. To isolate it, the cell must first be broken open. The enzyme used depends on what the cell wall is made of.
Option (1) Cellulase — Incorrect. Cellulase digests cellulose. Cellulose makes the wall of plant cells, so cellulase is used for plant cells, not for fungi.
Option (2) Lysozyme — Incorrect. Lysozyme breaks down the wall of bacterial cells. A fungal wall has a different chemical, so lysozyme does not open it.
Option (3) Chitinase — Correct. The cell wall of a fungus is made of chitin. Chitinase digests chitin, so the fungal cell opens and releases its DNA.
Option (4) Lipase — Incorrect. Lipase digests fats (lipids). It is not used to break any cell wall in DNA isolation.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Isolation of the Genetic Material (DNA) – “… Recall that nucleic acid is the genetic material of all organisms without exception. In majority of organisms this is deoxyribonucleic acid or 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).”