It does this by determining how evil the host is or if the host has the capacity to be evil, indeed. The really silly part is the fact that once inside a human host these alien chromosomes somehow are able to choose whether or not to turn the host into a monster or superhuman. Alien remains found on Mars with extra chromosomes allow humans to become immune to disease and heal faster, experimentation's on subjects cause them to mutate into monsters which of course break free and kill everyone. From there on the film goes off on its own tangent which encompasses all manner of regular sci-fi cliches. The plot flies close to the actual game story within the manual with certain aspects like the Mars location, teleportation experiments and the UAC corporation. Not that its a bad film though, surprisingly it keeps to the original source material and is actually made for adults only, one of its better qualities. We all know the game and how iconic it is, this film adaptation is less than iconic.

Doom get back to mars