8.4.11 Gel Electrophoresis

Process of Gel Electrophoresis

1. Preparation of Gel:

• Agarose gel is prepared and placed in a tray. Agarose is a porous material that allows fragments to move based on their size.

2. Loading the Samples:

• DNA samples are mixed with a loading dye to make them visible and to allow them to sink into the wells in the gel.

3. Setting Up the Electric Field:

• The gel is submerged in a buffer solution to maintain a stable pH.
• Electrodes are attached to opposite ends of the gel. The negative terminal (cathode) is near the wells, and the positive terminal (anode) is at the opposite end.

4. Separation of Fragments:

• When the current is applied, DNA (negatively charged due to its phosphate backbone) moves towards the positive electrode.
• Smaller fragments move faster and travel further through the gel, while larger fragments move more slowly.

5. Visualisation:

• The gel is stained with a DNA-binding dye (e.g., ethidium bromide or SYBR Green), which fluoresces under UV light.
• The DNA fragments appear as bands at different positions on the gel, depending on their size.

Applications of Gel Electrophoresis

6. DNA Analysis:

• Used to separate DNA fragments for genetic fingerprinting, paternity testing, and forensic investigations.

7. Checking PCR Results:

• Confirms the success of PCR amplification by showing the presence of the expected DNA fragment sizes.

8. Protein Studies:

• Separates proteins for Western blotting or to analyse the purity of protein samples.

9. Gene Cloning:

• Helps isolate specific DNA fragments for use in recombinant DNA technology.

10. Disease Diagnosis:

• Identifies genetic mutations by analysing DNA fragment patterns.