The Amateur Biologist


Kitchen sink biology

I go along with the received wisdom these days that this dawning era won’t be remembered as the computer century, but the biological century. What has been missing from this upcoming bio-revolution is the hands-on access of garage science. When it is as easy to program DNA in your bedroom as it is to program a chip, that’s when we’ll be swept off our feet in innovations. No reporting or speculative essay has given as much of a glimpse of this future than this how-to book of basement biology. Edited by former Amateur Scientist columnist Shawn Carlson (who also wrote many of the reprinted columns) this text tackles such old-time skills as cultivating pond scum (one source of commercially valuable microorganisms), or hacking up a video microscope, or measuring the heartbeats of insects. In the last section Carlson gets into how to extract DNA from cells using kitchen utensils. It’s wide open from there.

A kitchen laboratory includes most of the items needed to isolate DNA. A drinking straw, for example can be used to add alcohol to the solutions (a) and a coffee stirrer serves to spool the DNA (b).


The most wonderful private garden I have ever seen is tucked away behind a modest house in La Jolla, California, not far from where I live. The gardener is a British-born psychology professor and dear friend who sends me home with fruit and flowers each time I visit. Recently I noticed that two of his plants, though very different in shape, produced flowers the exact same shade of purple. This observation made me wonder whether the two species might be related.


One normally traces evolutionary connections by identifying physical similarities between species. So I decided to extract and isolate the pigments in the two flowers so that I could compare them in detail. That process is actually much easier than it sounds. In fact, using a simple technique called electrophoresis, I could carry out the experiment in about an hour for very little money.


DNA is the largest molecule known. A single, unbroken strand of it can contain many millions of atoms. When released from a cell, DNA typically breaks up into countless fragments. In solution, these strands have a slight negative electric charge, a fact that makes for some fascinating chemistry. For example, salt ions are attracted to the negative charges on DNA, effectively neutralizing them, and this phenomenon prevents the many separate fragments of DNA from adhering to one another. So by controlling the salt concentration, biologists can make DNA fragments either disperse or glom together. And therein lies the secret of separating DNA from cells.


The detergent actually does double duty. It breaks down cell walls and helps to fracture large proteins so they don't come out with the DNA. The people at Edvotek recommend using pure table salt and distilled water, but I have used iodized salt and bottled water successfully, and once I even forgot to add the baking soda and still got good results. In any case, try to avoid using tap water. To slow the rate at which the DNA degrades, it's best to chill the buffer in a bath of crushed ice and water before proceeding.


For a source of DNA, try the pantry. I got great results with an onion, and the folks at Edvotek also recommend garlic, bananas, and tomatoes. But it's your experiment: choose your favorite fruit, vegetable, or legume. Dice it and put the material into a blender, then add a litter water and mix things well by pulsing the blades in 10-second bursts. Or, even simpler, just pass the pieces through a garlic press. These treatments will break apart some of the cells right away and expose many cell walls to attack by the detergent.

An amateur s apparatus for measuring the metabolism of mice.

12/9/03 -- KK