Can I be DNA identified from my scab?

May 7, 2011 4:15 PM

DNA question plus *Gross-out alert* If you don't like real live scabs from injuries, read no further. It won't get any better. I'm guessing that I've thinned the clicking herd...

I took a non-spectacular fall about three years ago. What looked like a fairly mild scrape on my inner elbow turned into a bit more. My elbow swelled up over a few days, I bled and swelled quite a bit from what looked like a mild scrape initially and I'm guessing I suffered what was actually underlying muscle tissue damage. Didn't go to the doctor, recovered just fine. Anyway, I saved the scab that I picked off and it has been sitting on my right computer speaker for several years. I actually enjoy picking it up and holding it to the faint scar on my elbow, amused how it still matches up. It's about two inches long, but no more than a quarter inch wide at it's widest, and mostly nowhere near that wide but wide enough to still stay in one piece. My question is the following. After sitting in the open air for several years does this scab contain viable enough DNA to identify me? If I should disappear can I tell my wife to forget about the comb, tooth brush, etc. and have her just hand over my massive aged scab to identify my body should it surface in he future and should anyone still care?

posted by Rafaelloello to Health & Fitness (6 answers total)

I wouldn't be surprised. There should be white blood cells and likely epithelial cells there. If it's been kept dry the DNA should be reasonably well preserved.

Heck, you can PCR for certain markers from human remains that are hundreds of years old, or from mamoth bones kept frozen for (tens of) thousands of years.
posted by porpoise at 4:19 PM on May 7, 2011

Best answer: Yes, DNA is very stable unless there's something around that's actively trying to chew it up. Chances are that your scab brought some skin cells off with it (and maybe some white blood cells, but I'm not sure how assiduously they avoid being caught in a developing clot) which will have become nicely dehydrated, keeping the DNA stable. Unless it has been at very high temperatures or in bright sunlight for long periods (UV damages DNA), I'd expect enough to have survived for pretty reliable DNA fingerprinting.
posted by metaBugs at 4:33 PM on May 7, 2011

Also: you need to do far, far better than talking about scabs to gross out a biologist. We can show you stuff that'll make you ashamed to be organic.
posted by metaBugs at 4:38 PM on May 7, 2011 [36 favorites]

Seconding metaBugs. I've isolates DNA from all kinds of stuff, including 60 year old samples. Dried DNA is remarkably stable, and since most fragments used for conventional or real-time PCR DNA analysis are very small (fewer than 100 base pairs), even extensive fragmentation shouldn't be a huge deal. PCR is so good these days that we can pick up a single copy of a target, i.e. even if the great majority of your nucleic acids have been destroyed or damaged in some way, chances are there is still enough to match the scab to your DNA.
posted by halogen at 7:12 PM on May 7, 2011

You probably could. We assembled the Neanderthal genome from 38000 year old bone remnants.
posted by a robot made out of meat at 7:33 PM on May 7, 2011

Best answer: If I were told to do PCR off of that shit, I'd just incubate it with some protienase K, phenol extract it, and then run it through a thermocycler. Your scab would be plenty effective so long as it has stayed dry and wouldn't phase anybody.
posted by Blasdelb at 9:39 PM on May 7, 2011