When Vargas wrapped up his presentation, Jenner said, “Dr. McKay?” And to the newcomers, “Dr. McKay heads the experimental unit. Please keep in mind that his research is the fallback position and may never be deployed, even if successful.”
Zack got to his feet. Before he could begin, Jenner added, “Since your area is the least familiar to all of us, Doctor, I hope your materials will begin with basics.”
“Yes,” McKay said. Definitely brownie points. He picked up a marking pen and pressed the button that retracted the screen into the ceiling. Behind it was an old-fashioned whiteboard on which someone had written “I WANT FUCKING REAL COFFEE!” There was no eraser. Zack swiped his sleeve across the board, leaving a smear. The marking pen had gone dry. Toni looked like she was suppressing giggles.
Two pens later, when he got one that actually wrote, he drew a diagram, talking as he sketched.
“Sparrows inherit two copies of every gene in their bodies, one from each parent. We are trying to alter one or more of those genes in order to develop two separate and distinct gene drives. Let’s call a sparrow carrying one copy of any altered gene ‘capital G.’ The other copy of the gene, plus both genes in unaltered wild sparrows, ‘small g.’ If the altered gene is dominant, then usually inheritance will go like this through successive generations:
“As you can see, fifty percent of the offspring carry the altered gene. Now each of these birds mates with wild sparrows, who are all small g:
“Now only one-quarter of offspring carry the altered gene. In the next generation, it will be only one-eighth, until the genetically engineered change effectively dies out. But with a gene drive, the situation is different. A gene drive utilizes a so-called ‘selfish gene,’ which is a bit of parasitic DNA that circumvents the laws of normal inheritance. It gets itself propagated preferentially by pasting a copy of itself into the matching chromosome inherited from the other parent, so that all of the offspring carry two altered genes. By piggy-backing on a selfish gene, a gene drive always gets inherited, like this.”
He sketched another diagram, suppressing the insane idea to draw birds instead of letters. Too bad he hadn’t had Caitlin “prepare his briefing materials.”
“Then those birds mate, and every one of their fledglings carries the alteration, on through the generations.”
Zack turned back to the table. “A gene drive creates a ‘selective sweep,’ spreading like wildfire and so eventually wiping out all other versions of that gene. This is a known phenomenon, occurring both naturally and through lab creations pre-Collapse, although there it affected insects, not birds.”
One of the new captains said, “But Dr. McKay, what are these two gene drives you’re trying to create going to do?”
“I was coming to that. One of the gene drives we’re working on would hinder birds’ ability to carry RSA. The other—”
The captain interrupted him. “But you haven’t achieved that gene drive, have you? In fact, Monterey Base research hasn’t advanced on any of your three fronts.”
“Well—we get closer every week.”
Toni raised her eyebrow at this blatant exaggeration. The captain looked skeptical, or unimpressed, or something else that annoyed Zack. All at once a new thought hit him—was he in the middle of some sort of turf war between Jenner and HQ?
No way to know. He turned back to the board. “The other gene drive will render male sparrows sterile. The result will, eventually, be this.”
There was silence. His attempt to lighten the atmosphere had fallen as flat as his dead bird.
The captain said, “And just why hasn’t this gene drive succeeded so far?”
“The main difficulty of the complex gene drive is resistance to it that develops after a few generations of bird breeding. We’re hoping to get around that by combining three different gene drives, so that resistance by mutation is minimized. But obviously that’s a difficult task. Sometimes the alterations interfere with each other. The gene-editing tool doesn’t cut or insert where it’s supposed to. Or it cuts the target but doesn’t complete the delivery.”
Marianne Jenner said, “But… apart from the difficulties… May I ask questions, too?”
Zack braced himself. Marianne, undeterred by considerations of either rank or turf wars, was probably going to put her very capable finger on every reason that Zack’s research shouldn’t even exist.
She did. “I’m wondering how you can create a gene drive capable of being carried by more than one species of sparrow, since their genomes do differ.”
Zack said, “We’re piggybacking on RSA itself, which infects all species of sparrows, and only sparrows.”
Her voice rose. “You’re further altering the virus that killed so many people?”
“Yes.”
“What if your alterations—”
“We’re doing extensive testing.” Both of them, and probably everyone else in the room, knew that “extensive testing” wasn’t possible with their limitations of resources, personnel, time, birds. Zack was doing what he could with what he had.
Marianne said, “You mentioned pre-Collapse gene drives in insects. I’m sure you know that when the bacterium Wolbachia was used to create a gene drive to infect mosquitoes that carry malaria, the researchers also discovered that some strains of the bacteria were capable of transferring horizontally to other arthropods. What if your gene drive—either of your gene drives—jumps to other species and changes their reproductive biology?”
“I think,” Zack said, “that you already know it can’t jump to humans. And that the chances of it jumping to species more closely related to birds is small.”
“But not zero. Altered genes have been transmitted through bacterial and parasitic plasmids.”
“Yes. We are trying to build in safeguards.”
“Doctor—you know that isn’t possible.”
Zack hadn’t wanted to do this. But if he didn’t, his entire team might be shut down by HQ. And nobody present except Toni would know he was about to utter a half-truth. “It wasn’t possible in your time, Marianne. We know more now.”
She was silenced.
The visiting captain was not. “But even if this gene drive can’t jump species, wiping out all the birds on Earth will wreck the entire ecology, won’t it?”
As if it weren’t already wrecked. Zack put both palms flat on the table and leaned forward. “Look, I’ve tried to make clear that this is last-ditch, final-resort, hope-to-God-we-don’t-need-it research in case the work by the other two scientific units fails. We cannot stay cooped up for generations in the few remaining domes. Ninety-six percent of children being born aren’t immune to RSA, and we can’t even discover which six percent are immune without exposing our children to overwhelming odds of a horrible death. If someday the choice comes down to the death of all birds or the death of humanity, which would you choose? I know my preference. And what I want is for us to have the means to have a choice, if it comes to that. That’s what this research is about.”
“Thank you, Doctor,” Jenner said. “I think we’re done here. Captains, this way, please.”
The room emptied. Toni lingered, but Dr. Vargas called her aside to ask her something. When everyone had gone, Zack hunted for an eraser to wipe the board of his clumsy diagrams. There still wasn’t one.
As he used his hand to erase, smearing his palm with black ink, he saw that in the second diagram, he had misspelled “inheritance.”