History Main / XenoNucleicAcid

* ''VideoGame/{{Fallout}}'': In a world set after a nuclear war, there are bound to be countless genetic abnormalities out in the wasteland. However, one pre-war example would be the experiments performed in the Pan-Immunity Virion Project. In their goal to protect America's population from Chinese bioweapons, they created a retrovirus that could transform all the DNA in a host cell into a quad-helix structure, which they hoped would prevent diseases from taking hold. Their crowning achievement, however, is the Forced Evolutionary Virus. The FEV is described as a Megavirus with a protein sheath reinforced by ionized hydrogen that protects it from radiation. The virus has pre-programmed introns specified for the species it infects. It works by copying the host cell's DNA and placing the data into exons, which is taken back by the virus and then re-introduced into the host's cells alongside the introns, which induce the radical mutations the FEV is known for.[[note]]This is actually a case of ArtisticLicenseBiology; viruses, by definition, can't edit genetic material or replicate on their own.[[/note]]

It's common to hear the term "Alien DNA" in fiction. This can be justified in the case of HumanAliens; if they experienced a case of convergent evolution on a planet identical to Earth, or both species were just engineered by the same precursors, then their genetic material could conceivably have a similar composition to ours. However, in the case of StarfishAliens, it's almost guaranteed to be ArtisticLicenseBiology. This is especially true in the case of any [[HalfHumanHybrid human-alien hybrids.]]

* ''Film/{{Evolution|2001}}'': When Ira examines the microbes from an asteroid that fell to Earth, he finds that they have DNA with ten base pairs.

* ''Series/DoctorWho'' [[Franchise/DoctorWhoExpandedUniverse Expanded Universe]]: In the ''[[Literature/DoctorWhoMissingAdventures Missing Adventures]]'' novel ''The Man in the Velvet Mask'', two of the characters travel to Paris and scoff at the idea of DNA, finding it ridiculous that humans have two coiled-up snakes inside them.

* ''Series/BattlestarGalactica2003'': The Humanoid Cylons are a race of [[ArtificialHuman synthetic beings]]. Their DNA is completely artificial. {{Subverted}} in that they're still genetically compatible with humans and a genetic test would indicate they are indeed human, though they still identify as machines.

* ''Franchise/TheHitchhikersGuideToTheGalaxy'' features a race of aliens called the Haggunenons, whose DNA is descibed as "a quadruple-striated octo-helix" and is so chronically unstable that their bodies undergo evolution into a new form several times over lunch.

** SpaceMarines are made by implanting them with vat-grown organs derived from the genetic material of their superhuman Primarch, which greatly increases the growth of muscle and bone, along with other abilities like spitting acid and being immune to poisons. When a Marine dies, the Chapter's top priority is to retrieve the progenoid gland (the organ that creates all others, and hosts the genetic memory[[note]]Each Space Marine has two of them, but only one is extracted before they serve in battle; in hopes of getting strong genetic memories, the other is kept in until death[[/note]]) from their bodies, both to use them to make more Marines and to prevent them from falling into the hands of Chaos.

* ''VideoGame/{{Fallout}}'': In a world set after a nuclear war, there are bound to be countless genetic abnormalities out in the wasteland. However, one pre-war example would be the experiments performed in the Pan-Immunity Virion Project. In their goal to protect America's population from Chinese bioweapons, they created a retrovirus that could transform all the DNA in a host cell into a quad-helix structure, which they hoped would prevent diseases from taking hold. Their crowning achievement, however, is the Forced Evolutionary Virus. The FEV is described as a Megavirus with a protein sheath reinforced by ionized hydrogen that protects it from radiation. The virus has pre-programmed introns specified for the species it infects. It works by copying the host cell's DNA and placing the data into exons, which is taken back by the virus and then re-introduced into the host's cells alongside the introns, which induce the radical mutations the FEV is known for. [[note]] This is actually a case of ArtisticLicenseBiology; viruses, by definition, can't edit genetic material or replicate on their own. [[/note]]
* ''VideoGame/MassEffect'':
** Protheans are mentioned as having quad-strand DNA, which is unique among known species. [[spoiler: It's also how Shepard and company discover the Collectors are actually heavily modified Protheans in the second game.]]

** ''VideoGame/MassEffectAndromeda:'' The kett have an unusual DNA sequence, in part due to their method of reproduction: [[spoiler:Namely, stealing the best bits of alien genomes they find interesting and splicing it into their own.]] When Ryder tries scanning it, their omni-tool can't make head nor tails of it.

* ''VideoGame/StarCraft'' has the Zerg, who famously have the ability to [[PlayedStraight bypass]] [[NoBiochemicalBarriers biochemical barriers]] and [[TheAssimilator steal genetic material from their prey]], allowing them to rapidly evolve. Their alpha amino acids are said to have unique "R groups" that allow damaged cells to fuse with protein to repair themselves, and "survival of the fittest, nature red in tooth and claw" is apparently imprinted into them on the genetic level.

* ''Literature/WhateleyUniverse'': Tennyo, despite appearing human, [[HumanOutsideAlienInside has some very strange internal features.]] In particular, her DNA is completely alien and isn't even arranged in a helix. And that's without getting into the '''antimatter''' [[AlienBlood in her blood]].

* ''Film/{{Evolution}}'': When Ira examines the microbes from an asteroid that fell to Earth, he finds that they have DNA with ten base pairs.

Life on Earth either possess DNA or RNA in its cells. These are composed of multiple nucleobases made of nitrogen, oxygen, and hydrogen in different formations. These are connected to a backbone made of sugar (deoxyribose) and phosphates. In the case of DNA, which exists as a double helix, these nucleobases are adenine, cytosine, guanine, and thymine. They link together to form base pairs, which, barring coding errors or mutations, are consistently paired A-T and C-G. In RNA, which exists as a single strand, thymine is replaced with a similarly structured nucleobase called uracil.

[[folder:Film — Live-Action]]

* In ''Film/{{Evolution}}'', when Ira examines the microbes from an asteroid that fell to Earth, he finds that they have DNA with ten base pairs.
* In ''Film/TheFifthElement'', Leeloo's DNA is briefly shown containing numerous helices compacted together. A scientist also comments that she has 200,000 "memo groups" compared with the 40 of humans,[[note]]Or in the French version, 200 billions to the humans' four[[/note]] which is pure {{technobabble}}. These are supposed to be signs of Leeloo being a genetically engineered perfect being.
* The HalfHumanHybrid Sil from ''Film/{{Species}}'' is the product of human gametes matched with engineered gametes received from extraterrestrial transmissions. Sil grows from zygote to prepubescent girl in one day, then escapes from the lab and goes running around loose in society.

** In ''Literature/{{Incandescence}}'', the far-future galactic civilization of the Amalgam is so diverse that asking someone whether they're "a child of DNA" is weird and intrusive. The person who asks had found a new DNA-based species and thought it a rare curiosity, worth sharing.

* The Humanoid Cylons in ''Series/BattlestarGalactica2003'' are a race of [[ArtificialHuman synthetic beings]]. Their DNA is completely artificial. {{Subverted}} in that they're still genetically compatible with humans and a genetic test would indicate they are indeed human, though they still identify as machines.

* On ''Series/StarTrekDeepSpaceNine'', Sloane says that the cure for the Changeling virus uses adenine, radodine, lidestolinine, and asporanine.
* In ''Series/TheXFiles'', alien organisms are discovered that have two additional bases in their DNA.

* Depending on the continuity, ''Franchise/{{Transformers}}'' flip flops on what exactly it is that make up the Cybertronian equivalent of DNA, but often it's 'CNA', an abbreviation which can either stand for 'Cyber/Nano Algorithms' or 'Cybernucleic Acid' DependingOnTheWriter. Note that Cybertronians are MechanicalLifeforms.

* The Ukra-Tal, a race of worm-like aliens in the ''VideoGame/SpaceEmpires'' series, possess a triple-helix DNA which is said to baffle geneticists of other races.

* {{Discussed|Trope}} in ''Webcomic/SchlockMercenary'' while [[https://www.schlockmercenary.com/2013-06-25 researching]] an alien biosphere.

* {{Discussed|Trope}} in ''Webcomic/GrrlPower'' when Dabbler reveals how she can learn languages so quickly. She, like other succubi, has T.N.A (tri-helix nucleocarbonic acid), consisting of a double helix that contains the succubus genes and an extra helix from the father that can be selectively used to determine physical traits and help the succubus mate with so many different species. She and Sydney then waste no time in making "T&A" jokes.

* ''VideoGame/AssassinsCreed'': The Isu AbusivePrecursors were HumanAliens with triple-helix DNA. Fragments of this can be found in [[UnevenHybrid some humans]], distant descendants of Isu who interbred with their human servants.

** In ''Incandescence'', the far-future galactic civilization of the Amalgam is so diverse that asking someone whether they're "a child of DNA" is weird and intrusive. The person who asks had found a new DNA-based species and thought it a rare curiosity, worth sharing.

** ''Distress'' is set before FirstContact, but a CrazySurvivalist had genetic engineering to replace his own DNA with custom-designed nucleotides all the same, purely to improve his odds in some hypothetical space-plague apocalypse.

Neither of these could be the case with aliens. Xeno Nucleic Acid, or XNA, is a blanket term for any alternative biopolymers to DNA or RNA. This could mean the presence of other elements, different numbers of base pairs, a different overall structure, etc. Since aliens will likely have evolved in a very different environment, their genetic material could be unlike anything we've seen on Earth.