Top 10 Fun Facts for DNA Electrophoresis
Reproduced from Life
Life Technologies, Inc.
Rockville, Maryland 20849
Did you know:
- When preparing agarose for electrophoresis, it is best to sprinkle
the agarose into room-temperature buffer, swirl, and let sit at least 1
min before microwaving. This allows the agarose to hydrate first, which
minimizes foaming during heating.
- Electrophoresis buffer can affect the resolution of DNA. TAE (Tris-Acetate-EDTA)
buffer provides better resolution of fragments >4 kb, while TBE (Tris-Borate-EDTA)
buffer provides better resolution of 0.1- to 3-kb fragments. In addition,
use TBE buffer when electrophoresing >150 V and use TAE buffer with
supercoiled DNA for best results.
- Migration of DNA is retarded and band distortion can occur when too
much buffer covers the gel. The slower migration results from a reduced
voltage gradient across the gel..
- Loading DNA in the smallest volume possible will result in sharper
- You can preserve DNA in agarose gels for long-term storage using 70%
ethanol. [See Jacobs, D. and Neilan, B.A. (1995) BioTechniques 19, 892.]
- Electrophoresing a gel too "hot" can cause the DNA to denature
in the gel. It can also cause the agarose gel to deform. Cool the gel with
a small fan during the electrophoresis.
- For the Supercoiled DNA Ladder electrophoresed on <1% agarose gels,
add 2 1lg/ml ethidium bromide to the gel. Otherwise, smeared bands and
extra bands will be seen because of different degrees of supercoiling.
[See Longo, M.C. and Hartley, J.L. (1986) Focus 8:3, 3. (reprinted on page
63, this issue).]
- When glycerol-containing loading buffers are used in DNA samples electrophoresed
through acrylamide gels, smiling bands may be accentuated especially in
- On a polyacrylamide gel, DNA fragments having AT-rich regions migrate
slower than other DNA fragments of the same size. This anomalous migration
is enhanced at lower temperatures and disappears at high temperatures.
This anomalous migration is not observed on agarose gels. [See Stellwagen,
N.C. (1983) Biochemistry22, 6186.]
- The minimum amount of DNA detectable by ethidium bromide on a 3-mm-thick
gel and a 5-mm-wide lane is 1 ng. Do not exceed 50 ng of DNA per band on
a 3-mm-thick gel and 5-mm-wide lane.