DNA
From Memory Alpha, the free Star Trek reference.
Deoxyribonucleic acid (DNA) is the building block of life. It is the blueprint for a living organism and encodes amino acids for polypeptides which form proteins, which, when properly sequenced, form cellular pathways that together form the physical structure and anatomical characteristics of an organic lifeform.
By matching DNA gene types, Starfleet was able to identify Jono as Jeremiah Rossa. (TNG: "Suddenly Human")
If DNA is changed in some way, the host organism responds to the change by re-making itself in the form specified by the new DNA, often extremely rapidly. Semi-corporeal beings such as the Founders also had DNA though there is no evidence they had any cellular structure or indeed any cells.
In 2369, following clues developed by his mentor, Richard Galen, Jean-Luc Picard discovered evidence that an ancient race of humanoids had seeded many planets with their DNA billions of years earlier. The evidence suggested that Humans, Romulans, Klingons, Cardassians, and others may have far more in common than previously believed. (TNG: "The Chase")
- The result of Progenitor DNA being spread across the galaxy is the humanoid form itself. This DNA creates a tendency toward a specific external form. The similarity created allows even for inter-species reproduction between species that evolved quadrants apart. It should be noted that the internal workings even down to the base element of the blood can still be quite diverse.
[edit] Background
- As DNA was relatively unknown in the 1960s, Star Trek: The Original Series has no mention of this rather significant piece of medical science, even though DNA would have been well known in the 2260s according to Star Trek canon. It is also for this reason that Original Series episodes depended on other medical methods whereas DNA samples would have been the perferred choice. Such examples include the voice print identification of Kodos, seen in TOS: "The Conscience of the King", and a reference to "medical plates" during the examination of Peter Kirk in TOS: "Operation -- Annihilate!".
- Though we often see DNA or genome modifications being the cause of shapeshifting (TNG: "Genesis") and numerous other episodes, no such condition can exist. For example, if one were to receive a kidney transplant from a female, one would not immediately start to become female as a result of the foreign DNA. The Founders are never mentioned to alter their DNA as they shapeshift and routinely assume the form of inanimate objects which do not have DNA.
