“The test is called electrophoresis. It’s a process that uses electrical current to move particles through a fluid or, in our case, a gel.”
Victor snaps the lid off of the plastic soap dish then uses the knife to carve away each end, creating a U-shaped shell. He holds it up and rotates it. “This is the gel casting tray. The gel goes in here.” He picks up a slightly larger plastic container. “This is the buffering chamber.” He demonstrates how the smaller tray fits inside the larger one. “That alkaline solution I put in the fridge goes in here.”
I make a quick sketch of these items in my notebook and label them.
Victor rips into the packages of wire, cuts off an eight-inch piece of red and one of black, and then proceeds to strip off the coating at each end and attach the shiny copper tips to the alligator clips.
“It’s starting to look electrical.” I remember the new equipment in Miss P’s lab. There was a clear acrylic tray that had similar red and black wires attached to it.
Victor sets the wires aside and creates two strips of aluminum foil, which he folds over each end of the buffering chamber. “The aluminum foil makes the contact point on the buffering chamber,” he says.
He clips a black wire over the foil at one end of the chamber and the red wire over the foil at the other end. “Black is negative and red is positive.” He sets the contraption in the middle of the table. “That is pretty much all there is to an electrophoresis chamber.”
I turn it over and inspect it from all angles. It looks exactly like a plastic soap dish inside of a sandwich keeper, wrapped in aluminum foil and wired up. But even though it’s primitive, it closely resembles the one I saw shoved aside in Miss Peters’s lab. “Why does it need a current?” I ask.
“The current mobilizes the individual DNA strands, moving them through the gel. The smaller the strand the farther it will travel.”
“But you don’t plug it in, right?” I ask.
“Nope. Six nine-volt batteries will run this baby in about forty-five minutes.” Victor unwraps the economy pack of 9-volt batteries and builds a little battery pyramid—three batteries on the bottom (tops up) and two batteries on top (tops down) all plugged in to one another. This arrangement leaves one terminal open on each end. “In the field test you can’t always rely on having available power,” he explains. “So, you need an alternative.”
I sketch his battery arrangement in my notebook. “I didn’t know you could plug one battery into another.”
“It’s called connecting them in series.” Victor touches the alligator clips. “I won’t do it now, but all I have to do is clip the red side to the positive terminal on your stack of batteries and the black side to the negative terminal and voilà, electrical current.”
I check the time on my phone. It’s still early; Rachel and the chief are probably just arriving at the opera. We have plenty of time.
“Now we make the agarose gel.” Victor is standing near the microwave and mimes a slight mad-scientist expression as he tears open a small envelope of powder he retrieved from his briefcase. He taps the contents into a glass measuring cup that already contained distilled water. He stirs the two ingredients together for a minute then holds up the cup for my inspection.
“It’s cloudy,” I say, wrinkling my nose.
He pops the measuring cup into the microwave and heats it for a few seconds.
“We actually have to melt it to be sure all the particles are removed,” Victor says.
While the cup containing the gel is heating, I notice Victor applying tape to the open ends of the soap dish. “Wait. You just cut that off. Was that a mistake?”
“Hey. You’re paying atttention,” Victor says. “I like that.” He holds the plastic tray up, gesturing to how it is formed. “Remember, I said this is the gel casting tray. When we run the test the ends need to be open so the current can pass through the gel. But we need to tape the end until the gel forms into a solid.”
The microwave dings and he removes the measuring cup and pours the melted mixture into the tray. “This’ll take thirty minutes to set up,” he says. “Now we prep the samples.”
While Victor messes around with the buccal swabs and test tubes, I page back in my notebook, reviewing the notes I’ve made. “I had no idea there were so many steps.”
“Fortunately, I don’t have to run DNA every day. But in my lab I have a lot of high-tech stuff that streamlines this process,” he says.
I watch as he uses a drinking straw to pipe the buffering solution into the first two tubes. Then he hands me the straw and I add it to the last two tubes. “So what do you do every day?” I ask.
Victor shrugs. “Solve mysteries any way I can … and go to meetings.” He rolls his eyes. “You have no idea how many meetings. By the way, here’s one for you: Did you know human DNA is 50 percent identical to the DNA of a banana?”
“Is that why bananas are so a-peeling?”