The Technique of Gel Electrophoresis

Gel electrophoresis is a widely used technique in molecular biology to separate and analyze DNA fragments. It is based on the principle that DNA molecules are negatively charged due to the phosphate groups in their backbone, and hence, they migrate towards the positive electrode when an electric field is applied.

Procedure of Gel Electrophoresis:
1. Agarose gel preparation: Agarose, a polysaccharide derived from seaweed, is commonly used to create a gel matrix for electrophoresis. Agarose powder is dissolved in a buffer solution and heated to form a gel. The concentration of agarose determines the size range of DNA fragments that can be separated. Higher agarose concentrations lead to smaller pores and better separation of smaller DNA fragments.

2. Loading the DNA samples: The DNA samples, obtained after cutting the DNA with restriction endonucleases, are mixed with a loading dye that contains a tracking dye (usually a blue or orange color) and a dense material (such as glycerol) to allow easy visualization and loading of the samples into the gel.

3. Loading the gel: Small wells or indentations are created in the agarose gel using a comb. The DNA samples, mixed with the loading dye, are carefully loaded into these wells using a micropipette.

4. Electrophoresis: The gel is submerged in a buffer solution that facilitates the flow of electric current. When an electric field is applied, the negatively charged DNA fragments migrate through the gel towards the positive electrode. Smaller fragments move faster and migrate further through the gel, while larger fragments move slower and remain closer to the loading wells.

5. Visualization: After electrophoresis, the DNA fragments are usually stained with a fluorescent dye, such as ethidium bromide, which intercalates between the DNA bases and emits fluorescence when exposed to ultraviolet light. The DNA bands can be visualized and analyzed using UV transillumination or a specialized gel imaging system.

Result Interpretation:
The gel electrophoresis technique separates the DNA fragments based on their size. The restriction endonuclease digestion of DNA creates fragments of different lengths. After electrophoresis, the DNA fragments appear as distinct bands on the gel, with the smaller fragments migrating further than the larger ones. The separation pattern allows the determination of the size of the DNA fragments and provides valuable information for various applications, such as genetic mapping, DNA fingerprinting, and recombinant DNA technology.

Option c gel electrophoresis is used to seprate DNA fragments.