goes into the notches evenly so that all the wells created are of the same size. Check to make
sure that no bubbles get trapped on the comb.
13. Leave the gel to cool for 15 minutes.
14. After the gel has solidified, secure the gates into the “down” position if you are using a gated
tray. Or, turn the gel into the correct orientation for the self-sealing tray. Be careful that the
gel does not slide off the tray.
15. Place the gel (on the gel tray) into the gel box, resting it on the gel tray stand, so that the
sample wells created by the comb will be closest to the negative electrode (black) end.
16. Pour 1X electrophoresis buffer into the gel box and over the gel. The gel must be completely
submerged and a continuous volume of buffer should just cover the gel (about 5 mm of buffer
should cover the gel) and the electrodes. Too much buffer will result in a slower gel run. This
requires about 250–300 mL of buffer.
17. Wait until you are ready to load and run the gel, and then with the gel covered with buffer,
gently pull the comb out of the gel. Pull the comb straight up in one smooth motion.
18. Check to make sure the gel wells are not broken or cracked. The gel can be used immediately,
or it can be stored (with the comb still in the wells) in the gel box overnight at room
temperature or in the refrigerator for several days.
Thinking Like a Biotechnician
1. The agarose gel in this lab is prepared with 1X electrophoresis buffer, not water. What is the
reason water is not used?
2. A 7mm gel is recommended for most samples. What are the disadvantages of pouring a gel
thicker or thinner than 7mm?
3. E-gels are commercially prepared agarose gels that will run tiny volumes of samples (see
Figure 4.19). They require a special e-gel box setup. Go online and find companies that sell
e-gels. What concentrations are available, and how many sample wells do the gels have? How
much sample will the wells hold?
Figure 4.19. An e-gel cartridge.
Photo by author.
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Chapter 4 Laboratory Manual