DNA and Heat
Name: Katie Z.
I am in the 7th grade. I have
just successfully extracted DNA from uncooked collard greens using
kitchen items (blender,water, salt, meat tenderizer, alcohol). I also
cooked some of the greens and tested for DNA. However, the DNA that I think
I see is not clumping together like the uncooked.
My Question: Does heating a living thing change
its DNA and why or how?
This is good science! You are asking if DNA is changed
by heating a living thing. Let us take this question
apart because it shows you are a keen observer. First,
why do you think the DNA is changed? Because it no
longer clumps--so you made an observation on the
physical properties and you assume that something has
changed. Good thinking. You did not aks "does DNA
change when heating" which you could test with a
sample of your isolated DNA, but you asked "does it
change when heating a living thing" instead. That is
the correct question to ask because that is what you
did when you cooked the vegetable.
The answer is: yes, DNA is distroyed if a living thing
is heated: the cells of the organism are degraded by
the heat, and that liberates enzymes, called DNAses,
that eat away the DNA. So the cell destroys its own
DNA when it is dying. The long DNA strands are
degraded to short fragments, and these no longer clump
What would happen if you heat DNA that is already
purified? There would no longer be DNAses present.
Would it still change? You have all the tools to do
A good pair of hands, keen observations and the right
questions asked: you would make a good scientist!
If you would like to do more experiments like these, check
see what else you could do with your skills.
Heating breaks the bonds between the two stands of DNA...its called
Peter Faletra Ph.D.
Office of Science
Department of Energy
Click here to return to the Molecular Biology Archives
Update: June 2012