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Reverse Mutations
Name: Jenny W.
Status: Student
Age: 17
Location: N/A
Country: N/A
Date: N/A
Question:
I go to a high school that is
relatively untechnologically advanced, but have access to the
equipment in the forensics lab of a police department about 45
minutes away from where i live. For an independent research project I
caused a reverse mutation of the lacY and lacZ genes in two E. coli strains
that had been lactose intollerant. The mutation caused them to be able
to ferment lactose. I would like to further this experiment, but I am at
a loss as to what my next step should be.
What does recombinant DNA
involve? What equipment is needed to do it and how do you know what genes
a bacterium will accept and what ones will kill it? What DNA is the best
to try and introduce?
Replies:
Your first question: what does recombinant DNA
involve? This term is used for experiments where DNA
is artificially altered, and then put back in an
organism, in your case an E. coli.
There is not much equipment involved when you do the
transformation with competent E. coli cells. These you
can make yourself but you would need a centrifuge for
that, a waterbath, and the usual bacteriological
equipment that you obviously have (petri dishes,
incubator, etc.). You would need vector DNA which can
be purchased. Maybe a nearby microbiology department
could donate some.
The simplest experiment is to introduce a resistance
to an antibiotic. Antibiotics are compounds that kill
bacteria, but bacteria can become resistant to it.
They do this in two ways, either they mutate
spontaneously their own DNA in a special gene that
makes them resistant, or they take up DNA (this is
called transformation) that helps them become
resistant. You could do the following experiment:
compare the efficiency to become resistant to an
antibiotic by spontaneous mutation, versus
transformation. Check the exibit on 'antibiotics' in
the Virtual Museum of Bacteria
(www.bacteriamuseum.org/niches/hwfbacteria/antibiotics.shtml)
to do a bit of reading first.
Ask your supervisor which type of antibiotic, and
antibiotic-resistance gene (present on a plasmid) is
available to you.
Another experiment you could do is to see which
mutation is easier to introduce in E. coli, resistance
to the antibiotic or tolerance for lactose. You would
need to do some calculations to determine the
frequency of mutation.
Other suggestions for experiments you can also find in
the museum, see
www.bacteriamuseum.org/educational.shtml
Have fun with your bacteriology experiments!
Trudy Wassenaar
Curator of the Virtual Museum of Bacteria
Click here to return to the Molecular Biology Archives
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Update: June 2012
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