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| Southern Blot Analysis
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| by Sister Lens-of-Science You remember the scene: Scully needs to figure out whether the stuff in her veins and the alien matrix are the same substance. She does this nifty test and ends up with a cool-looking Chutes and Ladders graphic, which supposedly proves a match. Most* of us were watching, thinking "I don't know what that is, but hey, COOL." The SOUTHERN BLOT was named after M.E. Southern, a 20th century British biologist. Similar tests, developed later, were named in Southern's honor... well, sort of anyway. We now have a Western Blot, and a Northern Blot... you get the idea. This system of nomenclature, of course, leaves open the possibility of other, less-well-known analyses: the Slightly East of Southeast Blot, for example. Perhaps one day we'll be running a Pacific Northwest blot, or a Just A Couple Of Degrees Off True South Blot, or the Blot That Can't Navigate It's Way Out Of A Paper Bag, or, of course, the eponymously-named Blot That Really Should Have Stayed On The East Coast, But Got A Wild Hair When It Was In College And Ended Up In A Commune In Berkeley, And Isn't That A Waste After All That Expensive Education? Anyway, very simply, a SOUTHERN BLOT is a process used to move DNA segments from a gel solution to a filter sheet. In this simplified cartoon, two different single-strands of human DNA are bound to a membrane. In this example, sample A is from, say, Scully, and sample B is from someone who has never, ever, not even once, been in contact with either a) a frozen alien, b) any kind of black oil, or c) the city of Vancouver.  The membrane is incubated with a solution containing another single stranded DNA (say, from a transgenic bee or an alien chimeric life form, or a middle aged surfer or something. For example.)  A wash step removes any segments not tightly bound to the DNA on the membrane. Only DNA that matches exactly (say, for example, the non-human DNA with which one was injected during one's three-month long alien abduction, just to mention a common situation) will remain bound.   What remains is a single bound strand of DNA, which clearly indicates that one is, unfortunately about to turn into a giant lizard. Or lose an arm. Actually, come to think of it, we're not sure what this means, exactly. But we have just done an extremely precise test to prove it. So there you have it. The SOUTHERN BLOT. Use it for all those times when you absolutely have to have definitive proof of... something. Thanks to Lensie for permission to post this article. To view the accompanying Powerpoint presentation, go here. |
