If the Agent had blown up the moon a couple of decades earlier, Eve Moira wouldn’t have known about epigenetics. It was still a new science at the time she was sent up to the Cloud Ark. During her first years in space, when she and her equipment had been coddled in the most protected zones of Izzy and Endurance, she’d had plenty of time to bone up on the topic. Like most children of her era, she’d been taught to believe that the genome—the sequence of base pairs expressed in the chromosomes in every nucleus of the body—said everything there was to say about the genetic destiny of an organism. A small minority of those DNA sequences had clearly defined functions. The remainder seemed to do nothing, and so were dismissed as "junk DNA." But that picture had changed during the first part of the twenty-first century, as more sophisticated analysis had revealed that much of that so-called junk actually performed important roles in the functioning of cells by regulating the expression of genes. Even simple organisms, it turned out, possessed many genes that were suppressed, or silenced altogether, by such mechanisms. The central promise of genomics—that by knowing an organism’s genome, scientists could know the organism—had fallen far short as it had become obvious that the phenotype (the actual creature that met the biologist’s eye, with all of its observable traits and behaviors) was a function not only of its genotype (its DNA sequences) but also of countless nanodecisions being made from moment to moment within the organism’s cells by the regulatory mechanisms that determined which genes to express and which to silence. Those regulatory mechanisms were of several types, and many were unfathomably complex.