Question

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. The commonly used matrix is agarose which is a natural polymer extracted from sea weeds. The DNA fragments separate according to their size through sieving effect provided by the agarose gel. Hence, the smaller fragments move farther in the agarose gel. The separated DNA fragments can be visualised only after staining the DNA with ethidium bromide followed by exposure to UV radiation. Bright orange coloured bands of DNA can be observed. The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is known as elution. The DNA fragments purified in this way are used in constructing recombinant DNA by joining them with cloning vectors.

The DNA fragments formed by treatment with endonuclease are separated by.

• A. PCR
• B. Gel Electrophoresis
• C. Cloning
• D. Restriction digestion

Answer 1

Answer: (B)

Gel Electrophoresis

Answer 2

Elution refers to the process of extracting or separating a specific substance from a matrix or medium. In the context of the passage, elution refers to the step of extracting the separated bands of DNA from the agarose gel after gel electrophoresis. The DNA fragments that have migrated and formed distinct bands in the gel are cut out, and the DNA is then extracted from the gel piece. This extraction step is known as elution.