WET LAB DNA Barcoding: From Samples to Sequences - Northwest ...

WET LAB
Sometimes the amount of DNA in each band of the molecular weight standard
is also known, so that scientists can estimate the amount of DNA in their
samples. This is covered in more detail in Slide #19.
c. The DNA samples are in Lanes 2–10.
d. DNA gels are stained, in this case with a chemical called ethidium bromide,
to visualize the DNA.
e. Examples of the sizes of four molecular weight standard bands are shown:
5000 base pairs (bp), 2000 bp, 1000 bp, and 750 bp.
23. Ask students to estimate the sizes of the bands in Lane 2 (yellow
arrow). The bottom band is approximately 900 bp, while the band above
it is approximately 4500 bp. [Note: Lanes 2, 3, and 4 contain bands of
approximately 900 and 4500 bp.]
24. Show Slide #14, which reviews the steps involved in agarose gel
electrophoresis: making the gel, preparing your samples, loading your samples
onto the gel, running the gel, and visualizing the gel. If your students have
experience making and running agarose gels, you may wish to skip to Step
#33. If your students do not have experience making and running agarose
gels, you may wish to show one or more of the tutorial videos listed above
under Lab 3: Teacher Preparation.
Wet Lab: Slide #14
Using Bioinformatics: Genetic Research
Wells: Holes in a gel into which samples
are placed or “loaded.”
25. Show Slide #15, which reviews the first step: making the agarose gel. Tell
students that agarose is made from a chemical called agar that is isolated
from seaweed. Agar is also used as a thickening agent, and is what gives
many consumer products their characteristic texture, including many sauces,
puddings, and custards. The final product is similar in consistency to Jell-O ®
and, as with Jell-O ® , the agarose is melted and poured into a mold. A small
comb is placed in the liquid to form the holes or wells into which the DNA
will be loaded.
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©Northwest Association for Biomedical Research—Updated October 2012