“If there's so much more mtDNA than nuclear DNA, why isn't it used all the time for criminal profiling?” Bartholemew asked.
“Well, there's a catch. Typically, when you get a nuclear DNA profile, the chances of finding another person with that profile are one in six billion. Mitochondrial DNA stats are far less discriminating, because unlike nuclear DNA, you inherit mtDNA only from your mom. That means that you and your brothers and sisters all have the same mtDNA she does ... and that her mom and siblings do, and so on. It's actually fascinating - a female egg cell possesses tons of mitochondria, as compared to the sperm cell. At fertilization, not only are the few sperm mitochondria totally outnumbered, they're actually destroyed.” Skipper smiled brightly.
“Natural selection at its finest.”
“It's a pity you have to keep us around for that whole fertilization thing in the first place,” Bartholemew said dryly.
“Ah, but you should see what's going on next door to me in the cloning lab,” Skipper replied. “Anyway, my point is that mtDNA isn't helpful if you're choosing between two biological siblings to pinpoint a suspect, but it's a nice tool if you're looking to exclude someone nonrelated from an investigation. Statistically, if you test fifteen spots on the DNA strand, there are more than an octillion nuclear DNA profiles, which is awfully nice when you're in front of a jury and trying to pin down a particular individual. But with mtDNA, there are only forty-eight hundred sequences logged to date . . . and another six thousand reported in scientific literature. With mtDNA, you might wind up with a relative frequency of point one four or something like that . . . basically, a subject will share a profile with four percent of the world's population. It's not specific enough to nail a perp without reasonable doubt in front of a jury, but it would allow you to rule someone out as a suspect because he or she doesn't have that particular profile.”
“So if the mtDNA profile of the hair found on the victim's body doesn't match the one for Trixie Stone's hair,” Bartholemew said,
“then I can't link her to the murder.”
“Correct.”
“And if it does match?”
Skipper glanced up. “Then you've got reasonable cause to arrest her.”
* * *
The sun skipped the Alaskan tundra. At least, that's how it seemed to Laura, or why else would it be pitch-dark at nine in the morning? She anxiously waited for the flight attendant to open the hatch of the plane, now that they had landed in Bethel. It was bad enough that she had a fear of heights and hated flying, but this was only half a plane, really - the front end was devoted to cargo.
“How are you doing?” Daniel asked.
“Fantastic,” Laura said, trying to lighten her voice. “It could have been a Cessna, right?”
Daniel turned just as they were about to exit the plane and pulled up the hood of her jacket. He tugged on the strings and tied them under her chin, just like he used to do when Trixie was tiny and headed out to play in the snow. “It's colder than you think,” he said, and he stepped onto the rollaway staircase that led to the runway.
It was an understatement. The wind was a knife that cut her to ribbons; the act of breathing felt like swallowing glass. Laura followed Daniel across the runway, hurrying into a small, squat building.
The airport consisted of chairs arranged in narrow rows and a single ticket counter. It wasn't manned, because the lone employee had moved to the metal detector, to screen passengers on the outbound flight. Laura watched two native girls hugging an older woman, all three of them crying as they inched toward the gate. There were signs in both English and Yup'ik. “Does that mean bathroom?” Laura asked, pointing to a doorway with the word ANARVIK overhead.
“Well, there's no Yup'ik word for bathroom,” Daniel said, smiling a little. “That actually translates to 'the place to shit.' ”
The single door split off to the right and the left. The men's and women's rooms were not marked, but she could glimpse a urinal in one direction, so she walked the opposite way. The sinks were operated by push pedals; she pumped one to start the flow of water and then splashed some on her face. She looked at herself in the mirror.
If someone else walks into the bathroom, she thought, I will stop being a coward.
If the family outside has made it through security, to the gate.
If Daniel is facing forward, when I come out.
She used to play this game with herself all the time. If the light changed before she counted to ten, then she would go to Seth's after class. If Daniel picked up before the third ring, she would stay an extra five minutes.
She'd take these random occurrences and elevate them to oracles; she'd pretend that they were enough to justify her actions.
Or lack therof.
Wiping her hands on her jacket, she stepped outside to find the family still crying near the metal detector and Daniel facing out the window.
Laura sighed with relief and walked toward him.
* * *
Trixie was shivering so hard that she kept shaking off the quilt of dead grass Willie had used to cover them for warmth. It wasn't like a blanket you could just pull over yourself; you had to burrow down and think warm thoughts and hope for the best. Her feet still ached and her hair was frozen against her head. She was consciously awake - somehow she thought that sleeping was too close to the line
of being blue and stiff and dead, and that you might pass from one side to the other without any fanfare.
Willie's breath came out in little white clouds that floated in the
air like Chinese lanterns on a string. His eyes were closed, which meant Trixie could stare at him as much as she wanted. She wondered what it was like to grow up here, to have a snowstorm hit like this and to know how to save yourself, instead of needing someone to do it for you. She wondered if her father knew this sort of stuff too, if elemental knowledge about living and dying might be underneath all the other, ordinary things he knew, like how to draw a devil and change a fuse and not burn pancakes.
“Are you awake?” she murmured.
Willie didn't open his eyes, but he nodded the tiniest bit, and a stream of white flowed out of his nostrils.
There was a warm zone connecting them. They were lying two feet apart, with grass heaped in the space between their bodies, but every time Trixie turned his way she could feel heat conducting through the dried straw, pulsing like light from a star. When she thought he might not notice, she inched infinitesimally closer.
“Do you know anyone who ever died out here?” Trixie asked.
“Yeah,” Willie said. “That's why you don't make a cave in a snowbank. If you die, no one can ever find you, and then your spirit won't ever rest.”
Trixie felt her eyes get damp, and that was awful, because almost immediately her lashes sealed shut again. She thought of the ladders she'd cut on her arms, the way she'd wanted to feel real pain instead of the hurt gnawed on her heart. Well, she'd gotten what she wanted, hadn't she? Her toes burned like fire; her fingers had swollen like sausages and ached. The thought of that delicate razor blade being drawn across her skin seemed, by comparison, ridiculous, a drama for someone who didn't really know what tragedy was.
Maybe it took realizing that you could die to keep you from wanting to do it.
Trixie wiped her nose and pressed her fingertips against her eyelashes to dissolve the ice. “I don't want to freeze to death,” she whispered.
Willie swallowed. “Well. . . there is one way to get warmer.”
“How?”
“Take off our clothes.”
“Yeah, right,” Trixie scoffed.
“I'm not bullshitting you.” Willie glanced away. "We both get.
. . you know . . . and then huddle together."
Trixie stared at him. She didn't want to be pressed up against him; she kept thinking of what had happened the last time she was this close to a boy.