Free Winter Study by Nevada Barr Page A

down the tube full of gel — the lane —
with the same amount of pressure. I mean it’s not pressure, it’s
electricity. It’s called gel electrophoresis…”
“I get the idea,” Anna said. “All the DNA bowling balls are rolled down their individual lanes with the same amount of force.”
“Okay.
That will work. The lighter ones go farther along the gel tubes than
the heavier ones. When they all stop, you look at a readout; it looks
sort of like a shadowy version of the old computer punch cards. A
series of marks. Like on television when they lay one DNA readout over
the other and all the marks are exactly the same and — Bingo! — you’ve
got the criminal.
“The
lab at Michigan Tech has the DNA fingerprints for all of the wolves on
Isle Royale. Whenever there’s a kill, a biotech or one of the Winter
Study guys collects samples from the scat. Over time, they’ve built up
a database on each of the wolves. Those ‘fingerprints’ are now in this
smaller computer. When I put in the sample from the blood or the
follicles that we took today,” she nodded toward the wolf melting into
the newspapers at their feet, “I’ll be able to tell where he’s been —
at what kills — which pack he belonged to, if he’d ever been at another
pack’s kill, things like that.”
In
law enforcement, Anna often had to wait weeks for DNA tests to come
back, and the kind of detail Katherine was talking about was
exorbitantly expensive. Often, up to fifty separate tests had to be run.
“Interesting,” she said noncommittally.
Katherine
heard the skepticism and cast back over her words to see where she’d
gone wrong. When she wasn’t guarding, which she did whenever a member
of the opposite sex was in the room, she was easy to read. Emotions
passed just under the skin the way they do on the faces of very young
children, leaving ripples in the eyes and mouth.
“The PCR is a
portable
DNA fingerprinting device,” she said.
The machines Anna had seen that tested for DNA markers were huge, computers and other paraphernalia taking up entire walls.
“I
first worked with one in the Northwest. Salmon. The fishermen can take
only one kind and not the other, but you can’t tell which fish is which
by looking at them. We used an earlier version of the PCR. The reason
it can work is that it doesn’t do much. You set it to figure out just
one or two things. Like the DNA for the two species of fish. Both
fingerprints are known quantities and are already loaded in the PCR’s
computer. So when you feed it the new sample, all it has to do is
compare it with those already on file; it doesn’t have to figure out
anything.
“What
this PCR does is simply show me the readout, what kind of line the
balls make; that’s that wolf’s ‘fingerprint.’ All the ISRO wolves’
fingerprints are in this machine, so the fingerprint I get is compared
to the existing fingerprints. Each existing fingerprint represents a
wolf and each wolf has been assigned a number. I can look at my readout
and see that number such and such left my sample. Or, in this case,
is
my sample. Then I e-mail the lab at Michigan Tech and add my data to theirs. Then
they
can
look back in their files and see that my wolf — this wolf — ate a
moose, say, at Rock Harbor in the winter of 2005 because somebody
collected scat there at that time and its DNA matched the DNA I
collected. Do you see?”
She
looked so desperate Anna might have said she understood even if she
didn’t. “I get it,” Anna said. “We do it with regular fingerprints.
They’re run through a national database and, if they match up, we know
where our guy was when he left his print behind.”
Relieved,
Katherine went back to her machine. Anna watched for a while, but it
was a one-woman show. Returning to the wolf, she crouched near its
head. Fluids were beginning to seep from the corpse as it thawed.
Before the animal was anywhere close to room temperature, the bunkhouse
was going to smell like