Ask A Scientist Molecular Biology Archive

name         DNAlover
status      student
grade        6-8
location

Question -   Hello, I've found out about extracting DNA is
possible, on the internet and I wanted to show it to my teacher.
But she didn't believe me and asked me if I can prove it. There are
so many sites on how to extract DNA but never has a real proof
(only an explanation).
So do I need molecular microscope (?!)  or something to really look
and see if it is DNA?
If so, do you know where my isolated DNA can be looked at without
buying an instrument?
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Most of the standard DNA extraction procedures where the last step is often
twirling the gooey DNA polymer around a stirring stick of some sort and
pulling it out of solution have been shown by chemical analysis to be made
of DNA by chemical analysis.  If you search the internet, you should be able
to find multiple reputable sources that use procedures similar to the one I
imagine you have found.  By the way, scientists seldom "prove" anything.
But we do succeed in convincing reasonable people by both inductive and
deductive logic...once we have the data.  In your case your teacher should
be convinced by more than one citation of a reputable source that has
published the procedure.

Here is one reputable source...

http://gslc.genetics.utah.edu/units/activities/extraction/

pf
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There are many ways to verify your solution contains DNA, but most require
sophisticated instruments. Here are a couple of ways you could support the
conclusion you have isolated DNA.

This method requires a spectophotometer available in most university
research labs. When DNA is heated to 90 deg. C, the UV light absorption of
the DNA will increase at a wavelength of 260 nm. This is because the
complementary strands of DNA absorb more UV light when they are
single-stranded.

If your DNA sample is viscous (syrupy), if you add DNAse to your sample, the
the viscosity will decrease. The viscosity can be measure by sucking the DNA
up into a 1 mL pipet and measuring the length of time it takes for the DNA
to drain from the pipet by gravity. After exposure to DNAse, the smaller DNA
molecules will have a lower viscosity and therefore drain from the pipet
faster. DNAse can be purchased from Sigma Chemical Co.

Good luck,

Ron Baker, Ph.D.
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What do you expect to see when you look under the microscope.  If you think
you will see a series of A's C's T's and G's you will be disappointed.  It
will look like a mass of ropey goo.  What you will be seeing is a mass of
the DNA from millions of cells all tangled together.  There is so much DNA
you can see it without a microscope.

If you want a reliable easy way to extract DNA, go to the Genetic Science
Learning Center website at the University of Utah.  (You can google it).
They have an easy do it at home recipe.

Maybe you can convince your teacher to do it as a lab in class.

vanhoeck
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