A Predalien, one of the more obvious results of the DNA reflex.

The DNA reflex[1][2] is the term given to the process by which the species Xenomorph XX121 inherits certain characteristics from its host organism. The process accounts for the physical and perhaps even mental[3] variations apparent in some specimens of the creature.


"While the mechanism for this change has yet to be identified, it's likely that some host gene segments are capable of exerting greater influence over the Alien species than others."
Weyland Yutani briefing on the Runner's physiological differences (from Aliens versus Predator 2: Primal Hunt)

The DNA reflex accounts for alterations to the Xenomorph's basic form based on the genetic makeup of the host inside which it gestates. It is not entirely clear whether the process is intentional or simply an unintended side-effect of the way in which the Chestburster develops, constructed from the host's own cells.[4] However, given the way in which the changes to the adult Xenomorph are so successfully integrated into the creature, it seems highly likely that it is an intentional process. One suggested purpose for the DNA reflex is to help the adult Xenomorph adapt to the environment into which it will be born — by adopting characteristics of another organism that is hopefully native to that environment, the Xenomorph will be better suited to its surroundings. The assimilation of host DNA apparently also helps the developing creature to "hide" from its host's immune system.[5]

Embryos are thought to copy around 10-15% of the host's genetic code during their early development.[1] Among the most obvious physical traits inherited as a result of the process are general stature — whether bipedal or quadrupedal — and, in the case of Predaliens, mandibles and dreadlocks. It is unknown whether the DNA reflex leads the Xenomorph to take on other, less obvious attributes, such as any inherent genetic strengths and vulnerabilities the host organism may have.[2] It has also been theorized that the adult Xenomorph may adopt some mental traits from the host, such as general intelligence and certain instincts.[3] Examples put forward to back up this suggestion include Predaliens that have been seen to ritualistically mutilate their prey in a manner similar to Yautja.[6]

As a side-effect of the DNA reflex, Xenomorph genetic material is also transferred to the host. It is this transference that allowed United Systems Military scientists to clone a Xenomorph Queen aboard the USM Auriga; as a Queen had been gestating inside of Ellen Ripley during her time on Fiorina "Fury" 161, blood samples taken from her there and later recovered by the USM contained the infant Xenomorph's DNA. However, the immense complexity of the genetic assimilation process meant the creation of a viable Ripley/Queen clone pair took years of research and numerous failed attempts.

Behind the Scenes

While the idea of the Xenomorph adopting different characteristics dependant on its host was not seen until Alien3, the concept had actually always been a part of the creature's makeup and was first suggested during the development of AlienRidley Scott has stated that, while shaping the Alien's lifecycle, the pre-production team considered how the creature would take on a different appearance were it to gestate inside a different host.[7] The director has gone on to state that the creature in the first film is merely "the man-version of Alien".[8]


  • The DNA reflex has something of a real-world counterpart known as horizontal gene transfer, which entails the transfer of genetic material between organisms through means other than traditional reproduction. Horizontal gene transfer occurs mainly between single-celled organisms, but at least one parasitic vine, Boquila trifoliolata, seems to be capable of altering the appearance of its leaves to mimic its host (perhaps with the assistance of a microorganism, although research into this is still ongoing).
  • In the novelization of Alien: Covenant, David states that the hybridized creatures spawned by the black liquid pathogen inherit traits from their host organism, similar to the DNA reflex of the Xenomorph.[9] Indeed, it is possible this is where the species acquired its ability to likewise take traits from its host.


  1. 1.0 1.1 Sandy Schofield. Aliens: Rogue, p. 63 (1996), Bantam Spectra.
  2. 2.0 2.1 Weyland-Yutani Archives (2008), 20th Century Fox [Blu-ray]
  3. 3.0 3.1 S. D. Perry. Alien: The Weyland-Yutani Report, p. 25 (2014), Insight Editions.
  4. Dave Hughes, Lee Brimmicombe-Wood. Aliens, Vol. 2 #17, p. 43 (1993), Dark Horse International.
  5. S. D. Perry. Alien: The Weyland-Yutani Report, p. 19 (2014), Insight Editions.
  6. Aliens vs. Predator (2010), Rebellion, SEGA [Microsoft Windows].
  7. Richard Meyers. The Officially Authorized Magazine of the Movie Alien, p. 53 (1979), Warren Publishing.
  8. Mark Kermode, Ridley Scott, Jean-Pierre Jeunet, Dan O'Bannon, Ronald Shusett, Sigourney WeaverAlien Evolution (2001), Nobles Gate Scotland [DVD].
  9. Alan Dean Foster. Alien: Covenant, p. 191 (2017), Titan Books.
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