In the article, Holliday proposed a hypothetical enzyme he dubbed “maintenance methylase.” It would bind a methyl group to a cytosine that was adjacent to a guanine if and only if the corresponding doublet on the other side was already methylated.

It was all hypothetical. Maintenance methylase might not exist.

But if it did—$

Pierre looked at his watch; it was almost closing time. He photocopied the article, returned the magazine to Pablo, and went home.

That night he dreamed of Stockholm.

“Good morning, Shari,” said Pierre, coming into the lab.

Shari was dressed in a beige blouse under a wine-colored two-piece suit. She’d cut her long, dark hair recently and was now wearing it fashionably short, parted on the left, and curving in toward her neck at the bottom. Like Pierre, Shari was burying herself in her work, trying to get over the loss of Howard.

“What’s this?” she said, holding up an autorad she’d found while tidying up. The lab would have been a pigsty if it weren’t for Shari’s periodic attempts to restore order.

Pierre glanced at the piece of X-ray film. He tried to sound nonchalant.

“Nothing. Just garbage.”

“Whoever this DNA belongs to has Huntington’s disease,” said Shari matter-of-factly.

“It’s just an old sheet.”

“It’s yours, isn’t it?” asked Shari.

Pierre thought about continuing to lie, but then shrugged. “I thought I’d thrown it out.”

“I’m sorry, Pierre. I’m so sorry.”

“Don’t tell anyone.”

“No, of course not. How long have you known?”

“Few weeks.”

“How is Molly taking it?”

“We — we’ve broken up.”

Shari put the film in a Rubbermaid garbage pail. “Oh.”

Pierre shrugged a little.

They looked at each other for a moment. Pierre’s mind did what he supposed every male’s did in moments like these. He thought for an instant about him and Shari, about the possibilities there. Both of them carried diseased genes. He was thirty-two and she was twenty-six — not an outrageous difference. But — but there were other gulfs between them. And he saw on her face no indication, no suggestion, no inkling. The thought had not occurred to her.

Some gulfs are not easily crossed.

“Let’s not talk about it,” said Pierre. “I — I’ve got some research I want to share with you. Something I found in the library last night.”

Shari looked as though she wanted to pursue the subject of Pierre’s Huntington’s further, but then she nodded and took a seat on a lab stool.

Pierre told her about the article in Scientific American; about the two forms of cytosine, the regular one and the 5-methylcytosine variant; and about the hypothetical enzyme that could turn the former into the latter but would do so only if the cytosine in the CG doublet on the opposite side of the strand was already methylated.

“Hypothetically,” said Shari, stressing the word. “If this enzyme exists.”

“Right, right,” said Pierre. “But suppose it does. What happens when DNA reproduces? Well, of course, the ladder unzips down the middle, forming two strands. One strand contains all the left-hand components of the base pairs, maybe something like this…” He wrote on the blackboard that covered most of one wall:

Left side: T-C-A-C-G-T

“See that CG doublet? Okay, let’s say its cytosine is methylated.” He went over the pair again with his chalk, making it heavier:

Left side: T-C-A-C-G-T

“Now, in DNA reproduction, free-floating nucleotides are plugged into the appropriate spots on each strand, meaning the right-hand side of this one will end up looking like this…”

His chalk flew across the blackboard, writing in the complementary sequence:

Left side: T-C-A-C-G-T

Right side: A-G-T-G-C-A

“See? Directly opposite the left-hand CG pair is the right-hand GC pair.” He paused, waiting for Shari to nod acknowledgment of this. “Now the maintenance methylase comes along and sees that there isn’t parity between the two sides of the strand, so it adds a methyl group to the right-hand side.” He went over the GC pair, making it darker, too:

Left side: T-C-A-C-G-T

Right side: A-G-T-G-C-A

“At the same time, the other half of the original strand is being filled in with free-floating nucleotides. But maintenance methylase would do exactly the same thing to it, duplicating cytosine methylation on both sides, if originally present on one side.”

Pierre clapped his hands together to shake off chalk dust. “Voila! By postulating that one enzyme, you end up with a mechanism for preserving cytosine-methylation state from cell generation to cell generation.”

“And?”

“And think about our work on codon synonyms.” He waved vaguely at the wall chart labeled “The Genetic Code.”

“Yes?”

“That’s one possible additional level of coding hidden in DNA, if the choice of which synonym used is significant. Now we’ve got a second possible type of additional coding in DNA: the code made by whether cytosine is methylated or not. I’m willing to bet that one or both of those additional codes is the key to what the so-called junk DNA is really for.”

“So what do we do now?” asked Shari.

“Well, as Einstein is supposed to have said, ‘God is subtle, but malicious he is not.’” He smiled at Shari. “No matter how complex the codes are, we should be able to crack them.”

Pierre went home. His apartment seemed vast. He sat on the living-room couch, pulling idly at an orange thread coming unraveled from one of the cushions.

They were making progress, he and Shari. They were getting close to a breakthrough. Of that he felt sure.

But he wasn’t elated. He wasn’t excited.

God, what an idiot I am.

He watched Letterman, watched Conan O’Brien.

He didn’t laugh.

He started getting ready for bed, dumping his socks and underwear on the living-room floor — there wasn’t any reason not to anymore.

He’d been reading Camus again. His fat copy of the Collected Works was facedown on one of the couch’s orange-and-green cushions. Camus, who had taken the literature Nobel in ‘57; Camus, who commented on the absurdity of the human condition. “I don’t want to be a genius,” he had said. “I have enough problems just trying to be a man.”

Pierre sat down on the couch and exhaled into the darkness. The absurdity of the human condition. The absurdity of it all. The absurdity of being a man.

Bertrand Russell ran through his mind, too — a Nobel laureate in 1950.

“To fear love,” he’d said, “is to fear life — and those who fear life are already three parts dead.”

Three parts dead — just about right for a Huntington’s sufferer at thirty-two.

Pierre crawled into bed, lying in a fetal position.

He slept hardly at all — but when he did, he dreamt not of Stockholm, but of Molly.