Question

In the isolation of DNA, removal of protein and RNA, is carried out by enzymes ________ and __________ respectively.
A. Ribosome , Ribonuclease
B. Protease ,cellulose
C. Protease, Ribonuclease
D. Ribonuclease, Chitinase

Answer 1

Hint:-"Separation of DNA by the destruction of cellular and nuclear membranes by chemicals, enzymes or physical disruption is defined as DNA extraction." DNA extraction is carried out by destroying the cell wall and nuclear membrane, followed by deproteinization and deposition of nucleic acids with ethanol. Friedrich Miescher first isolated DNA in 1969.

Complete Answer:-Isolation of DNA
DNA is obtained from cells by the most gentle method to prevent mechanical shear DNA fragmentation.
This usually occurs in the presence of EDTA, which chelates Mg2+, which is required for an enzyme that breaks down DNA called deoxyribonuclease (DNase). Ideally, the cell wall, if present, should be digested enzymatically (e.g. treatment of lysozyme with bacteria) and the cell membrane should be diluted with detergent.
Removal of RNA-After the nucleic acid is released from the cell, the RNA can be removed by treatment with ribonuclease (RNase), which has been heated to remove the DNase contaminant, because RNase is stable when heated due to its disulfide bonds, and the molecule recovers rapidly when cooled.
Removal of Protein-Another major contaminant, protein, is removed by gently shaking the solution with a water-saturated phenol or phenol / chloroform mixture, followed by treatment with Proteinase K. Both the treatments are denatures only protein not nucleic acid.
Other molecules are removed by suitable treatment and purified DNA is finally precipitated after addition of chilled ethanol.
Centrifugation of the solution separates the accumulated cell debris from the DNA. Purification of DNA from detergents, proteins, salts and reagents used during the cell lysis phase.


So the correct option is (C).

Note:- The diphenylamine (DPA) indicator confirms the presence of DNA.
If DNA is needed from cell organelles or viral particles, it is better to isolate cell organelles or virus particles first, because DNA from DNA mixtures is difficult to obtain. If a high degree of purity is required, the DNA can undergo an ultracentrifugation density gradient via caesium chloride, which is very useful for plasmid DNA preparation.