The massive/tiny scale of ancient DNA

varma_tuco

Wild tuco-tuco. Photo by Anand Varma, former member of my lab; http://www.varmaphoto.com/

Take a tooth. Leave it in a cave for 5000 years. Retrieve it and examine the tooth: after all that time, those seasons passing and bacteria working away, what is left of the original animal? Not a lot; but not nothing.

There remains still some DNA from the original owner of the tooth, but degraded, fragmented into little pieces, and overwhelmingly outnumbered by the DNA of all the bacteria that have grown and reproduced and died in the tooth. Finding the DNA of the original animal would be like finding a needle in a haystack—if the haystack was really big and the needle was also a piece of hay, just slightly different from all the other hay.

And yet: we can do it.

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Blood secrets

Sometimes doing science feels like doing magic. Take a fantastical witch brewing eye of toad and nightshade flower in a cauldron, substitute a 1.5 ml tube for the cauldron, AW1 Buffer for the nightshade flower, and blood of junco for the eye of toad, and that’s me.

(And that “eye of ___” thing happens in science too: a few of my herpetologist colleagues have been talking lately about what you can learn from preserved lizard eyes.)

One of the things I do when I capture a junco is to collect a blood sample. I use a sterile needle, collect very little blood, and don’t let the bird go until I’m sure the bleeding has stopped. The birds usually don’t even flinch. They act much more upset when I blow on their chests to look for brood patches (I think it feels cold to them) than they do when I take blood.

Me collecting blood from GRAY. The blood moves up the tiny capillary tube on its own. Photo by M. LaBarbera.

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White gloves, strange rooms

One of the things I like about what I do is the strangeness of my everyday situations. There’s more of the boring old Sitting At A Computer Situation than I would like, but the Measuring Baby Birds On A Mountaintop Situation helps make up for that.

Now that field work is (mostly) over for the season, my situations are different, but not really less strange.

Strange Room #1

In order to look at the genetics of the juncos, I’ve been doing lab work in the Museum’s Evolutionary Genetics Lab. Lab work was my introduction to ornithology as an undergrad, and I’ve always liked it, despite the bleach and the potentially-toxic chemicals and the way my nose always itches and I can’t scratch it because I’ve got latex gloves on. The colors, noises, and vocabulary of lab work are specialized and surreal: the stacks of plastic racks in bright red, yellow, blue; the whirr of centrifuges starting up, like tiny revving plane engines; aliquot, vortex, elution buffer. I like the contrariness of refrigerators and microwaves with NO FOOD scolded across them. The concentration required to pipette the right amounts of the right reagents into the right tubes again and again and again makes it a kind of meditation.

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