🧪 General Principles🟢 BasicMolecular Biology Techniques

Electrophoresis

A laboratory technique that separates molecules such as DNA or proteins by pulling them through a gel with an electric field, sorting them by size and charge.

Key points

Electrophoresis separates charged molecules by making them move through a gel in an electric field, the migration depending on size, charge and shape; in size-based gels the smaller molecules travel further.
DNA and RNA carry a negative charge, so they move towards the positive electrode, and they are sorted mainly by size in an agarose gel.
Proteins can be separated on a polyacrylamide gel, and in SDS-PAGE a coating of negative charge makes them separate mainly by size.
Serum protein electrophoresis separates the blood proteins into bands (albumin and the globulins), and the pattern helps detect disease.
A sharp extra band (an M band) in the gamma region indicates a monoclonal protein (paraprotein), which can occur in several conditions such as MGUS, multiple myeloma and other plasma-cell or B-cell disorders.
Haemoglobin electrophoresis separates the types of haemoglobin and is used to diagnose sickle cell disease and the thalassaemias.

Memory trick

Charge and size decide the race: negative DNA runs to the positive end, SDS-PAGE sorts proteins by size, and an M band flags a monoclonal protein.

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🧪 General Principles🟢 BasicMolecular Biology Techniques

Electrophoresis

A laboratory technique that separates molecules such as DNA or proteins by pulling them through a gel with an electric field, sorting them by size and charge.

Key points

Electrophoresis separates charged molecules by making them move through a gel in an electric field, the migration depending on size, charge and shape; in size-based gels the smaller molecules travel further.
DNA and RNA carry a negative charge, so they move towards the positive electrode, and they are sorted mainly by size in an agarose gel.
Proteins can be separated on a polyacrylamide gel, and in SDS-PAGE a coating of negative charge makes them separate mainly by size.
Serum protein electrophoresis separates the blood proteins into bands (albumin and the globulins), and the pattern helps detect disease.
A sharp extra band (an M band) in the gamma region indicates a monoclonal protein (paraprotein), which can occur in several conditions such as MGUS, multiple myeloma and other plasma-cell or B-cell disorders.
Haemoglobin electrophoresis separates the types of haemoglobin and is used to diagnose sickle cell disease and the thalassaemias.

Memory trick

Charge and size decide the race: negative DNA runs to the positive end, SDS-PAGE sorts proteins by size, and an M band flags a monoclonal protein.

All of Biochemistry More General Principles