Agarose gel electrophoresis

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Agarose gel electrophoresis setup

Agarose gel electrophoresis is a method used in biochemistry, molecular biology, and clinical chemistry to separate a mixed population of macromolecules such as DNA or RNA fragments, or proteins, based on their size and charge. This technique is widely used for the analysis of nucleic acids and proteins.

Principle

Agarose gel electrophoresis works on the principle of separating molecules by size through a gel matrix. The gel is made from agarose, a polysaccharide extracted from seaweed. When agarose is dissolved in a buffer and allowed to cool, it forms a gel with a network of pores. The size of these pores can be controlled by adjusting the concentration of agarose.

Procedure

The procedure involves several key steps:

1. Preparation of the Gel: Agarose is dissolved in a buffer solution and heated until completely melted. The solution is then poured into a casting tray and allowed to solidify.
2. Loading Samples: Samples are mixed with a loading dye and carefully pipetted into wells in the gel.

   File:Loading DNA samples into an agarose gel for electrophoresis - CPHST - USDA photo.jpg

   Loading DNA samples into an agarose gel

3. Running the Gel: The gel is placed in an electrophoresis chamber filled with buffer. An electric current is applied, causing the negatively charged DNA molecules to migrate towards the positive electrode.
4. Visualization: After electrophoresis, the gel is stained with a dye such as ethidium bromide or SYBR Green to visualize the DNA bands under ultraviolet light.

   

   Agarose gel under UV light

Applications

Agarose gel electrophoresis is used in various applications, including:

• DNA Analysis: To check the quality and quantity of DNA, to separate DNA fragments for cloning, and to analyze PCR products.
• RNA Analysis: To assess RNA integrity and to separate RNA molecules for further analysis.
• Protein Analysis: Although less common, agarose gels can be used to separate large proteins or protein complexes.

Advantages and Limitations

Agarose gel electrophoresis is a simple, cost-effective, and versatile technique. However, it has limitations, such as lower resolution compared to polyacrylamide gel electrophoresis and the inability to separate very small DNA fragments effectively.

Related Pages

• Electrophoresis
• Polyacrylamide gel electrophoresis
• DNA ladder
• Gel electrophoresis of proteins

Gallery

• 
  Two percent agarose gel in borate buffer
• 
  Plasmid DNA ready for electrophoresis
• Video: Assembling the rig and loading the gel
  Video: Assembling the rig and loading the gel
• DNA moving along the gel
  DNA moving along the gel
• Cutting the agarose gel
  Cutting the agarose gel