Gel Electrophoresis

Question 1

Step one

Answer 1

A tray is prepared to hold the gel matrix

Question 2

Step two

Answer 2

A gel comb is used to create holes in the gel. The gel comb is placed in the tray.

Question 3

Step three

Answer 3

Agarose gel powder is mixed with a buffer solution (this stabilises the DNA). The solution is heated until dissolved and poured into the tray and allowed to cool.

Question 4

Step four

Answer 4

A gel tray is placed in an electrophoresis chamber and the chamber is filled with buffer solution, covering the gel. This allows the electric current from the electrodes at either end to flow through the gel.

Question 5

Step five

Answer 5

DNA samples are mixed with a ‘loading dye’ to make the DNA sample visible. The due also contains glycerol and sucrose to make the DNA sample heavy so it will sink to the bottom of the well.

Question 6

Step six

Answer 6

The gel is covered, electrodes are attached to a power supply and turned on.

Question 7

Step seven

Answer 7

When the dye marker has moved through the gel, the current is turned off and the gel is removed from the tray.

Question 8

Step eight

Answer 8

DNA molecules are made visible by staining the gel with methylene blue or ethidium bromide which binds to DNA and will fluoresce in UV light.

Question 9

What impacts the rate of movement of the DNA?

Answer 9

1. size of DNA fragments
2. amount of electrical current
3. concentration and agarose gel
4. time left in gel chamber

Question 10

What is gel electrophoresis?

Answer 10

A technique that separates fragments of DNA according to their size and charge.
DNA has an overall negative charge. Agarose gel acts as a large sponge through which the DNA strands move when in the influence of an electric current.
Negatively charged DNA moves towards positive electrode and are repelled by negative electrode.
DNA its self is not visible so methylene blue or a ethidium bromide is used as a DNA binding dye that appears fluorescent under UV light.