gregated and regulated based on the "purity" of their DNA at birth; over the course of their lives, their mutation levels are checked periodically. Unauthorized gene-editing or deviation from the approved human genome is punishable. Due to the environment unstability, everyone is exposed to mutagens which slowly change their human genome, but gene stabilizers can keep your DNA "pure" and "perfect" – if you can acquire and use them, that is. The "pure" ones live in the higher levels of the Spires and they enjoy the gene stabilizers provided by the government. They are perfect in every sense of the word. The ones from the lower levels are not so lucky: they have to fight for the gene stabilizers or find other ways to survive.