In the near future, the Earth experiences an unprecedented ice age, resulting in the downfall of modern civilization, as temperate zones become glacial, food supplies fail, and those who can flee towards the warm equatorial zone. Ten years later, John Starkman is one of the rugged few who chooses to live isolated in the ice and snow, eking out a marginal survival. After years of not seeing another living soul, a strange ship approaches on the horizon, and picks him up, willing or not.
He learns that in the past few years, representatives of the Galactic Empire have come to Earth and are transforming it so it can still support the surviving humans. They've eliminated most disease, provided food and jobs to all, and stabilized the political chaos which plagued the end of civilization. John's suspicious nature can't accept that all of this is being done out of the goodness of the alien's hearts (or whatever is equivalent in their biology) and looks for ways to rebel at every turn. It's only when a doctor gives him a mandatory but routine blood test that the curtain starts to be lifted away, and he gets drawn deeper and deeper into hidden factions and is forced to solve the mystery that unwittingly centers on him.
While the Chomosomal Code is an entertaining read overall, following the successful formula of a fugitive on the run, who's unsure who he can really trust, the biggest flaw in the book is that for the most part, Starkman is simply running from one crisis to another, and not really ever getting the chance to take matters into his own hands. The highlight of the book though is the actual explanation of what causes these events to come to pass, taking several sci-fi tropes and neatly explaining them in a way that surpasses most stories that include them in a neat little package.