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Tuesday, November 30, 2004

How to extract your own DNA

Courtesy of Radio Wales this morning - swill your mouth out rigorously with salty water. Spit the solution into a glass containing washing up liquid diluted with water. Add cold, strong gin. After a few minutes the washing up liquid will start to separate and thin white spirals of DNA will become evident. Awesome.

Comments:
I'm afraid this sounds like another example of bad science in the media yet again. The naked eye can see objects down to about 50-100 micrometers (0.05-0.1 millimeters or 0.00005-0.0001 meters) The diameter of an average human cell is about 10 micrometers. Each individual human cell contains 23 paired chromosomes. A single chromosome is a very long DNA molecule and associated proteins. The diameter of the DNA helix is 2 nanometers or 0.002 micrometers and although its length could be between 1.7 - 8.5 centimeters fully stretched, in the cell it is usually several thousand times shorter. What all this means is that I think it is highly unlikely to be DNA that can be seen. If it is anything biological then it is more likely to be large proteins. Someone please correct me if I'm wrong, but I can't see how the DNA itself would clump together into a large enough mass to be seen with the naked eye. As part of good scientific methodology it would be interesting to know what would happen if the salty water wasn't used to swill your mouth out, but the rest of the steps were followed (i.e. salt water added to washing up liquid diluted with water, and then gin added). This would be known as a control and would see if the thin white spirals were really anything to do with your mouth (and hence your cells and/or saliva) or not. Science can still be awesome though.
 
It seems that it does clump together enough to be seen. Check out this:

http://www.nature.ca/genome/05/051/pdfs/DNAextract_e.pdf

(a PDF, of course)

and this

http://gslc.genetics.utah.edu/units/activities/extraction/
 
Ahhh, now it makes sense; it's always nice to learn something new. With regard to the initial posting, I suppose I'm very skeptical of anything that tells you the steps to take but not why you are taking them. All too often 'science' that is utter nonsense can be found on the internet (as well as other sources).
 
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