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Our DNA contains the genetic recipe for making us who we
are. It controls what we look like and can influence our propensity for
contracting some diseases. Each strand is only about 50 trillionths of an inch
long, but did you know that you can painlessly extract a visible amount of your
own DNA in the comfort of your kitchen? All you'll need is a buffer
solution, a couple of drinking glasses, a paper clip, and some spit.
A buffer solution works in several ways. It breaks open
the cheek cells floating around in your saliva so that the DNA is released. It
keeps the strands from clumping together too quickly. It deteriorates the
proteins surrounding your DNA. And it has just the right pH balance for your
DNA to thrive—a too-acidic or too-alkaline solution would destroy it.
Here's a simple recipe for a buffer solution that
you can make in your kitchen and a list of other items you'll need. If
you're under 18, you should ask an adult to help.—Rima Chaddha
Ingredients
1/2 cup distilled or bottled water
1/4 tsp salt
1 tsp baking soda
1 tsp of detergent
1 drop pineapple juice
1 oz 90% isopropyl alcohol (chilled in freezer
beforehand)
Tools
1 spoon
1 paper clip
2 drinking glasses
Your spit
Procedure
Add the distilled or bottled
water to one of your drinking glasses. (Tap water contains impurities that can
damage extracted DNA.) Use the spoon to stir in the salt
and baking soda until they've completely dissolved in the water. The salt
will prevent your DNA from bunching together before it has separated from surrounding
proteins, and the baking soda will give the solution a neutral pH. Mix in a teaspoon of detergent
and just a drop of pineapple juice. The soap will break down your cells and
liberate your DNA, while the juice destroys the proteins surrounding it. Take a small amount of
water—not
your buffer solution—and slosh it around in your mouth for about 30
seconds. Then spit into the empty glass. You now have a fresh collection of
cheek cells from which you can harvest your DNA. Pour some of the buffer solution
into the glass containing your saliva. You should add about twice as much
buffer as you have spit and water. Stir gently. You should now have
a soup of DNA, broken cells, and proteins all mixed together. Gently pour the isopropyl alcohol
down the side of the glass so that it sits on top of the mixture. This should
be straightforward, because alcohol is less dense and therefore lighter than
your buffer solution and saliva. Let the mixture stand for two
minutes. You will soon see strands of DNA floating up toward the alcohol. Remove the DNA from the solution
by unbending your paper clip to look like a hook and then gently swirling it
around the alcohol to collect the strands, which gathered together will
resemble a translucent slime.
Remove the clip and voila! You've just successfully
extracted your own DNA. Although a single strand is too small to be seen by the
naked eye, you can see your DNA here because you've collected a lot of it
from a large number of cells. When the strands left the cheek cells, they
intertwined into larger, more visible masses.
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