Question

Which of the following is the purpose of gel electrophoresis?

• A. Construction of recombinant DNA by joining with cloning vectors
• B. Separation of DNA fragments according to their size
• C. Cutting of DNA into fragments
• D. Isolation of DNA molecule

Answer 1

The correct option is B

Separation of DNA fragments according to their size

The correct option is B.

Explanation of correct option:

1. The technique of gel electrophoresis is used to separate DNA (Deoxyribonucleic acid) fragments based on their size and charge.
2. The process begins when DNA fragments are placed into wells on one end of a gel, and an electric current is used to draw it through.
3. Negatively charged DNA pieces move toward the positive electrode.
4. Small DNA fragments pass through the gel faster than large fragments because all DNA fragments have the same amount of charge per mass.
5. When a DNA-binding dye stains a gel, the DNA fragments appear as bands, and each will be represented as a group of identical-sized DNA fragments.

Explanation of incorrect options:

Option A:

1. After ligation, genes contained in restriction endonuclease-extracted DNA fragments can be retained and expressed by inserting them into cloning vectors.

Option C:

1. Restriction enzymes are a type of enzyme that recognizes a specific sequence of nucleotides and cuts DNA into fragments.
2. Restriction endonucleases are another name for restriction enzymes.

Option D:

1. In molecular biology, alkaline lysis is a technique for isolating plasmid DNA.
2. Circular plasmid DNA in bacteria is most often isolated by alkaline lysis, and even RNA can be isolated with this method.

Final Answer: The purpose of gel electrophoresis is the separation of DNA fragments according to their size.