 Subject 20's genetic design incorporates human DNA, and its method of killing is to inject its prey with the Proto B DNA strain which then proceeds to remove all genetic differences within specific cells.The result is that the victim's living body slowly erodes into gelatinous pile of pure protein which Subject 20 consumes for sustenance.After its final mutation, where the creature evolves into a huge insect-like being with a large mouth full of sharp teeth, the creature is slain when it eats Cal's cancer-ridden liver, its body genetically self-destructing from within.