Fallout creator Tim Cain continues to release videos on various topics. Recently, he decided to discuss some mechanics from the original game.
The focus was on FEV (Forced Evolutionary Virus) radiation. Tim clarified that he is stating his thoughts; now the canon is determined by Bethesda, so his ideas have no value.
To explain how "Radiation" works, he talked about the structure of DNA: it consists of a double helix of four purines A, T, C, G, which are connected in pairs "A — T", "C — G".
If one of the purines is knocked out, the body can easily recover. However, if radiation knocks out both purines in a pair, a problem arises: the body does not know how to recover from such damage.
If such a damaged cell continues to function with an error in the genetic code, it will produce incorrect proteins, which can lead to cancer if the protective mechanisms do not destroy it.
Tim concluded: "That's how it happens in real life and we thought: \"Okay, that's how radiation will work in Fallout\"".
Then, the Forced Evolutionary Virus was invented for Fallout, which works differently. Like all viruses, it "inserts genes into the [host] cell" and forces it to reproduce copies of the viral genome. A distinctive feature of FEV is that it turns the double helix of DNA into a quadruple helix.
The source of inspiration for the developers was the book "Elise: A Terrifying Novel of Immortality": the story of a girl whose father was poisoned and as a result she was born with a quadruple helix of DNA, becoming "eternally young".
The idea of the Fallout authors was that the quadruple helix is more resistant to radiation, since instead of knocking out two purines, you need to knock out four — this is statistically extremely unlikely.
And the developers also added "infertility". The main character of Fallout could deal with the Master by proving the infertility of super mutants: the quadruple helix will divide into a double helix and it will not have a mechanism for recombination, i.e. super mutants cannot have children and will eventually die.