“At the usual time,” Kevin said. Then after a brief hesitation, he surprised himself by adding: “I might have company. Would that be a problem?”

“Not at all,” Esmeralda said. “How many persons?”

“Just one,” Kevin said. He hung up the phone and wiped his palms together. They were a little damp.

“Are we on for lunch?” Candace called from across the room.

“Let’s go!” Kevin said.

“This is some lab!” she commented. “I never would have expected to find it here in the heart of tropical Africa. Tell me, what is it that you’re doing with all this fantastic equipment?”

“I’m trying to perfect the protocol,” Kevin said.

“Can’t you be more specific?” Candace asked.

“You really want to know?” Kevin asked.

“Yes,” Candace said. “I’m interested.”

“At this stage I’m dealing with minor histocompatibility antigens. You know, proteins that define you as a unique, separate individual.”

“And what do you do with them?”

“Well, I locate their genes on the proper chromosome,” Kevin said. “Then I search for the transponase that’s associated with the genes, if there’s any, so I can move the genes.”

Candace let out a little laugh. “You’ve lost me already,” she admitted. “I haven’t the foggiest notion what a transponase is. In fact, I’m afraid a lot of this molecular biology is over my head.”

“It really isn’t,” Kevin said. “The principles aren’t that complicated. The critical fact few people realize is that some genes can move around on their chromosome. This happens particularly in B lymphocytes to increase the diversity of antibodies. Other genes are even more mobile and can change places with their twins. You do remember that there are two copies of every gene.”

“Yup,” Candace said. “Just like there are two copies of each chromosome. Our cells have twenty-three chromosome pairs.”

“Exactly,” Kevin said. “When genes exchange places on their chromosome pairs it’s called homologous transposition. It’s a particularly important process in the generation of sex cells, both eggs and sperms. What it does is help increase genetic shuffling, and hence the ability of species to evolve.”

“So this homologous transposition plays a role in evolution,” Candace said.

“Absolutely,” Kevin agreed. “Anyway, the gene segments that move are called transposons, and the enzymes that catalyze their movement are called transponases.”

“Okay,” Candace said. “I follow you so far.”

“Well, right now I’m interested in transposons that contain the genes for minor histocompatibility antigens,” Kevin said.

“I see,” Candace said, nodding her head. “I’m getting the picture. You’re goal is to move the gene for a minor histocompatibility antigen from one chromosome to another.”

“Exactly!” Kevin said. “The trick, of course, is finding and isolating the transponase. That’s the difficult step. But once I’ve found the transponase, it’s relatively easy to locate its gene. And once I’ve located and isolated the gene, I can use standard recombinant DNA technology to produce it.”

“Meaning getting bacteria to make it for you,” Candace said.

“Bacteria or mammalian tissue culture,” Kevin said. “Whatever works best.”