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Name: Katie Z.
Status: Student
Age: 13
Location: N/A
Country: N/A
Date: N/A 


Question:
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?



Replies:
Katy,

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 together.

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 the experiment. 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 out

http://www.bacteriamuseum.org/educational.shtml

to see what else you could do with your skills.

Trudy Wassenaar


Heating breaks the bonds between the two stands of DNA...its called "denaturing"

Peter Faletra Ph.D.
Office of Science
Department of Energy



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