Gel Electrophoresis

  • Define gel electrophoresis: A technique used to separate DNA fragments (or other macromolecules, such as RNA and proteins) based on their size and charge

  • Describe what happens during the process of gel electrophoresis: Charged molecules respond to the current by moving from the sample wells into the gel. Negatively charged molecules move toward the anode, positively charged molecules move toward the cathode.

  • Identify the tools used to perform gel electrophoresis and their respective functions:

    • Staining and visualization: Gels are stained with ethidium bromide to visualize DNA fragments.

    • Gel: Made of agarose, it is used for DNA electrophoresis.

    • Tank: Holds the gel during electrophoresis.

    • Comb and micropipette: Used for loading DNA samples onto the gel.

    • Power supply: Maintains constant conditions for electrophoresis.

    • Buffers: Establish pH and electrical charge.

    • Electrophoresis chamber: Holds the gel during electrophoresis.

    • Electrodes: Provide current for DNA migration.

    • Gel Caster and Comb: Used for loading DNA samples onto the gel.

  • Describe how an electric current drives the movement of DNA (or proteins) during gel electrophoresis: During gel electrophoresis, an electric current is used to pull DNA molecules. The DNA fragments are separated by size, with smaller fragments moving fastest towards the electrode. The force that moves the DNA is an electric field.

  • Explain how gel electrophoresis can be used as evidence in criminal cases or in paternity tests: In a criminal case, it’s used to help catch criminals. While in paternity tests, its used to help see who the father (50% of the DNA in the fragments) of a child is by separating DNA by size.

  • Explain the role of restriction enzymes during gel electrophoresis: Restriction enzymes: They cut DNA, RNA, or plasmid at specific recognition sites (restriction sites) to create smaller genetic fragments. These fragments can then be separated and characterized using gel electrophoresis. Different restriction enzymes recognize and cut different DNA sequences. Restriction enzymes are proteins isolated from bacteria and act as molecular scissors to cut the genetic code.

  • Distinguish between anode and cathode:

    • Anode: Where oxidation occurs; usually the positive side; electrons move into the external circuit.

    • Cathode: Where reduction occurs; usually the negative side; electrons are given out

  • What is the gel electrophoresis technique used for? Separating molecules (DNA strands and proteins) according to their length.

  • What is the power supply function? Produce an electric current in the electrophoresis chamber.

  • What is the buffer solution’s function? Carry the electric current.

  • Which electrode is further from the wells? Positive electrode

  • Which fragment of DNA is further from the wells? Smallest fragments