Echoes Of Honor

'I believe that probably constitutes at least a one or two thousand percent understatement, Your Grace,' Allison said wryly. 'One of the things which has puzzled those of us who have studied the situation has been how your colony could possibly have survived for more than a generation or two amid such lethal concentrations of heavy metals. Obviously, some sort of adaptive change had to have occurred, but none of us could understand how it happened quickly enough to save the colony. Now, I think, I know.'

She took a sip of tea and crossed her own legs, leaning back in her chair and cradling the tissue-thin porcelain cup between her hands.

'Heavy metals enter the body via the respiratory and digestive tracts, Your Grace, hence your air filtration systems and the constant battle to decontaminate your farm soil. Apparently, whoever was responsible for this—' she jutted her chin at the holo image once again '—intended to build a filtration system into your bodies as well, by modifying the mucosal barriers in your lungs and digestive tract. Your secretory proteins are substantially different from, say, my own. They bind the metals—or a large proportion of them, at any rate—which allows them to be cleared from the body in sputum and other wastes, rather than being absorbed wholesale into the tissues. They don’t do a perfect job, of course, but they’re the reason your tolerance for heavy metals is so much higher than my own. Up until two or three months ago, the assumption, particularly in light of your ancestors’ limited technological resources and, um, attitude towards the resources they did have, was that this must represent a natural facet of adaptive evolution, even if we had no idea how it had happened so quickly.'

'But you no longer believe this to be the case,' Sullivan said quietly.

'No, Your Grace. I’ve found flanking regions of rhinovirus genetic material around the cystic fibrosis locus indicated in the holo here, and I think I can say with some assurance that it didn’t get there accidentally.'

'Rhinovirus?'

'The vector for the common cold,' Allison said dryly, 'which could have offered several useful advantages to the med teams who made use of it. For one thing, with your people so tightly confined in the limited air-filtered habitats they could build, an aerosol vector like this would be very easily spread. Given the fact that I’ve found absolutely no mention of it anywhere in the records, I might also hazard the guess that the project was kept confidential at the time—possibly to avoid raising hopes if, in fact, it should fail. Or there could have been other reasons. And if there were, spreading the alteration via ‘a cold’ would have the advantage of maximum concealability, as well.'

'Indeed it would have, and there could well have been ‘other reasons’ to do such a thing quietly,' Sullivan agreed, and it was his turn to smile crookedly. 'Despite my own analysis of why Father Church does not believe in suppression, not everyone in our history would have agreed with me, and no doubt there have been times when our freer thinkers found that... discretion was indicated. As I’m sure you’ve discovered in the course of your research, My Lady, many of our Founders were zealots. Heavens, look at those lunatics who launched the Civil War four hundred years later! However trying our own times may be, they do not compare to the Tests which faced the Founders, and it would certainly have been possible that the Founding Elders might have feared that some of the more blindly faithful among their flock would have reacted badly to the notion of such a thing as permanently modifying their own bodies and those of all their descendants.'

'As you say, Your Grace,' Allison murmured, then shrugged. 'At any rate, we might think of this as a sort of weapon of beneficent biological warfare, an agent designed to modify the genetic material of your people in order to give them a fighting chance at surviving their environment. Unfortunately, it looks like it was a fast and dirty method, even by the standards of then-current technology.'

Sullivan frowned, and she shook her head quickly.

'That wasn’t a criticism, Your Grace! Whoever managed this was clearly working on a shoestring, with limited resources. He had to do the best with what he had, and what he managed was brilliantly conceived and clearly executed effectively. But I suspect that the need for speed, coupled with extremely limited facilities, prevented his team from carrying out as careful an analysis as they would have wished, and it looks like the vector carried a second, unintentional modification which they failed to recognize at the time.'

'Unintentional?' Sullivan’s frown was deeper now, not in displeasure but in thought, and Allison nodded.

'I’m certain it was. And the nature of their problem no doubt helps explain what happened. You see, whoever designed this modification had to make the adaptive mutation inheritable. Simply modifying the gene in those actually exposed to the rhinovirus wouldn’t work, because it would have been a purely somatic mutation, which means it would have died with the first generation of hosts. To keep that from happening, he—or they—had to cross from the somatic to the germ line—modify the rhinovirus to cross the mucosal barrier and show a predilection for primordial germ cells in the host’s ovaries and testes—in order to pass it on to the first generation’s offspring. What had to be accomplished was analogous to, oh, the mumps virus. That infects the salivary glands, but also attacks the ovaries and testes and can account for some cases of male infertility.'

Sullivan nodded to indicate understanding, and Allison hid another mental smile. Interesting that he showed no discomfort at all with the way the conversation was headed. Of course, with the high percentage of stillborn boys on this planet, Graysons had been fanatical about prenatal care for centuries, and men were just as involved in the process (at one remove, of course! she amended) as women.

'They had no real option about that,' she went on. 'Not if they wanted the change to be a permanent addition to the planetary genome. But in the process, they also got an unintended mutation. Their intervention introduced a stable trinucleotide repeat on the X chromosome, which wouldn’t have been a problem... except that it in turn affected one of the AGG codons.' Sullivan looked blank. 'AGG codons are adenine-guanine-guanine sequences that act as locks on the expansion of other trinucleotide repeats,' she explained helpfully.

'Of course,' Sullivan agreed. He didn’t look too terribly enlightened, but he nodded for her to continue, and she punched a new command into her holo unit. The imagery changed to a color-coded schematic of nucleotides—an enormous chain composed of the color-coded letters 'A,' 'C,' 'G,' and 'T,' repeating again and again in jumbled patterns. As Sullivan watched, the image zoomed in on a single section—two three-letter groups of 'CGG' in yellow, green, and green, separated by an 'AGG' in red, green, and green.

'Essentially, it was a very tiny change,' Allison told the Reverend. 'An adenine here—' she touched another key, and one of the 'AGG' codes flashed brilliantly '—mutated to cytosine—' another key, and the flashing red 'A' turned into a yellow 'C' and the three-letter group to its right grew suddenly into an enormous chain of the same codes, repeating again and again '—which deactivated the lock and allowed unstable expansion of—'

'Excuse me, My Lady,' Sullivan interrupted, 'but I think we’re drifting into deep water here. What, precisely, does that m— No.' He stopped and raised one hand. 'I’m certain that if you told me what it meant, I would be no closer to understanding than I am now. What I truly need to know, I suppose, is what the consequences of this... unstable whatever are.'

'Um.' Allison sipped some more tea, then shrugged.

'DNA is composed of four nucleotides, Your Grace: adenine, cytosine, guanine, and thymine. They link together in thousands of repeats—codes, if you will—which combine to carry the blueprint for our bodies... and transmit it to the next generation. They link in groups of three, hence the term ‘trinucleotide,’ which usually occur in ‘runs’ of thirty or less, but there are several diseases, such as the one we call ‘Fragile X,’ in which the number of repeats expands enormously, often into the thousands, effectively... well, scrambling a portion of the master code, as it were. Are you with me so far?'

'I believe so,' he said cautiously.

'All right. This schematic represents a portion of the nucleotides—in this case cytosine, adenine, and guanine—from the Grayson genome. This trinucleotide here—' she touched her controls and the holo reverted to its original form with the 'AGG' flashing once more '—is what we call a ‘lock,’ sort of a blocker to prevent the CGG repeats on either side of it from expanding in a way that would scramble the code. What happened, though, was that when the adenine mutated into cytosine, the ‘lock’ disappeared... and that allowed an unstable expansion of the CGG chain ‘downstream’ of it.'

'I won’t pretend to understand completely, My Lady,' Sullivan said after a moment, 'but I believe I understand the process, in general terms at least. And just how serious a problem is this ‘unstable expansion’?'

'Well, in Fragile X, the consequence is—or was, before we learned to repair it—moderate mental