Regeneration




 * This article is about the Time Lord physiological process. For the non-fiction book see Doctor Who: Regeneration

Regeneration is the process by which the Time Lords maintain their centuries-long lifespans. It is generally described as a "genetic reshuffling" which a Time Lord may go through if his or her body is worn out by age or has suffered some life-threatening injury or infection. Time Lords may even regenerate at will.

The regeneration process
During regeneration, the body of a Time Lord is reconfigured into a new form; the new form is generally physically younger and healthier (in human terms) than the Time Lord's previous incarnation. After each regeneration there is a marked change in a Time Lord's appearance and personality. During the process of regeneration there are the genetic equivalent of 'bit errors' appear in the DNA of the regenerated cells. This is what causes the appearance of the Time Lord to change; because even the cells of the brain regenerate as well, their brain chemistry and organisation will change. Although the aspects of their personality caused by "nurture" will not change, the "nature" contribution to their personality will change. (BFA: The Sirens of Time)

The actual regeneration is a painful process as bones and tissue settle into their new forms. (DWN: The Power of the Daleks) The Time Lord will often suffer from confusion, erratic behavior and memory loss. (DW: Castrovalva, The Twin Dilemma, The Christmas Invasion) During the first few hours of the regeneration, the Time Lord will be unstable mentally and physically. If they are knocked unconscious, the whole process might be started all over again. (DWN: The Power of the Daleks) After a while, the Time Lord's body will have settled down, though they can regrow limbs within the first 15 hours of the regeneration due to having enough residual energy. (DW: The Christmas Invasion) Some Time Lords, however, may regenerate with little or no overt complications, for example, Romana. (DW: Destiny of the Daleks).

Regeneration posture
While most of the Doctor's regenerations have occurred with him in a prone position, it appears that, when possible, Time Lords try to regenerate while standing up, with their arms outstretched to their sides and looking up. This posture was demonstrated by the Doctor as he regenerated from his Ninth to Tenth incarnations, (DW: The Parting of the Ways) and prepared to regenerate into an Eleventh incarnation after being injured by a Dalek (DW: The Stolen Earth). The Master, in his Professor Yana incarnation, adopted an identical posture as he regenerated into the incarnation that would come known as Harold Saxon. (DW: Utopia). It is worth noting that most of the Doctor's regenerations occurred due to injury or other condition that left him unconscious or otherwise unable to stand on his own. ''Two other on-screen Time Lords known to have regenerated are Romana and Borusa, but none of their regenerations occurred on screen; neither did the regenerations of the Second and Eighth Doctors; they might have also regenerated while standing. K'anpo Rimpoche regenerates in Planet of the Spiders while slumped in a chair.''

TARDIS and Regeneration
A TARDIS may have some effect on the regeneration process. The Doctor's regenerations that have taken place outside the TARDIS have generally been more 'difficult' than others. Two (his second and third regenerations) were controlled by or required the intervention of another Time Lord, another (his fourth) required an extended period of rest in the TARDIS zero room, and the last (his seventh) was arguably the most difficult, since the Doctor was effectively dead for several hours before the regeneration was triggered. Of the regenerations that took place within the TARDIS, one (the first) occurred with very few side effects, another (the fifth) resulted in severe mental instability for an extended period, another (the sixth) resulted in brief post-regenerative amnesia, and the last (the ninth) resulted in a synaptic implosion that caused a period of unconsciousness and was cured by some tea. When the Master regenerated in Utopia, he struggled to enter the TARDIS before triggering the process, and the Doctor ordered his companions to bring him into the TARDIS before his aborted regeneration in The Stolen Earth. It is possible that being within a TARDIS may somehow facilitate or ease the regeneration process.

Limitations
It was established that a Time Lord can regenerate successfully twelve times before permanently dying. (DW: The Deadly Assassin) As with most such "rules" there were occasionally exceptions to the twelve regeneration limit and it may be circumvented through unorthodox means. The Master, after taking over the body of a Tremas, is offered "regeneration: a whole new life cycle" as an incentive to rescue the four Doctors from the Death Zone. (DW: The Five Doctors)


 * Alternatively, this might just imply that a cycle of regenerations can be given to non-Time Lords.

The Doctor's arch-enemy, the Master, found his own remedy for the end of his regenerative cycle. He first attempted and failed to use the Eye of Harmony on Gallifrey to renew himself, though he was able to absorb enough energy from it to extend his life for a time. (DW: The Deadly Assassin) He was finally able to gain access to the Source on Traken, and used some its powers to steal the body of Nyssa's father Tremas. (DW: The Keeper of Traken) When this body was finally destroyed by the Daleks on Skaro, the Master's essence entered that of a human on Earth, and in this body the renegade Time Lord tried to use the powers of the Eye of Harmony's dimensional link on the Doctor's TARDIS to steal the Doctor's remaining lives. (DW: Doctor Who: The TV Movie)

Rassilon is said to have achieved a cycle of perpetual regeneration, becoming immortal. It was for this secret that Lord President Borusa sent four of the Doctor's incarnations and their companions into the Death Zone, where Rassilon lay in eternal sleep in the Dark Tower. (DW: The Five Doctors) It may also have been this particular method of perpetual regeneration which Mawdryn and his team of scientists attempted to steal from the Time Lords, with the result that they became undying creatures who continually aged and regenerated until the Doctor was able to finally help them die. (DW: Mawdryn Undead) Legends suggest that Rassilon became immortal when he was turned into a vampire by the Great Vampire himself. (MA: Goth Opera)

There are many indications that regeneration is not a guarantee. The Doctor, for example, was at one point convinced that he was going to die at the hands of the Gelth (DW: The Unquiet Dead) and there have been numerous occasions in his lifetimes where survival -- including regeneration -- is not assured. A very sudden death may also make it impossible to regenerate, (DW: Turn Left) implying that a Time Lord must either be able to actively concentrate to start their regeneration, (for example, DW: The Parting of the Ways) or must not be in a environment that would prevent regeneration (for example, DW: Time and the Rani when regeneration occurs while the Doctor is unconscious, but still within the TARDIS). It is also known that the interference of some medications, such as anesthesia, may disrupt or destroy the regenerative process. (DW: Doctor Who: The TV Movie)

Control over regeneration
Generally, regeneration is initiated when a Time Lord has been too badly injured to survive. However in some cases Time Lords have been known to exercise control over the process. Romana appeared to regenerate on a whim, when The Doctor inquires what she is doing she replies casually 'regenerating' and emerges from the rear of the TARDIS with a new appearance (DW: Destiny of the Daleks). The Time Lord Azmael initiated a thirteenth regeneration in order to end his life (DW: The Twin Dilemma). The process can also be stopped with some difficulty (DWN: The Power of the Daleks), as the Master did in order to spite the Doctor (DW: Last of the Time Lords).

The degree of control that Time Lords have over their end appearance is unclear. The Master was able to make his next regeneration as young as the Tenth Doctor. (DW: Utopia) Romana seemed adept enough at the process to custom design her new appearances, trying several bodies before finally deciding on a copy of Princess Astra. The Doctor criticizes Romana for taking on the form of another person, suggesting such things are not unheard of and it's considered bad form to copy someone else. (DW: Destiny of the Daleks) In contrast to Romana, the Doctor does not appear to have much control over his post regeneration appearance; after his fourth regeneration he commented "that's the problem with regeneration, you never quite know what you're going to get". (DW: Castrovalva)

Regenerations can also be forcibly prevented after fatal injury by force of will, probably leading the Time Lord in question to die of their injuries. (DW: Last of the Time Lords).

The Time Lords were apparently capable of controlling the regeneration of individual Time Lords, either forcing a regeneration (DW: The War Games) or removing later regenerations (DW: The Trial of A Time Lord).

Aborted Regeneration
Occasionally, a regeneration will fail and the regeneration will abort. Though Time Lord technology can treat this, in some occasions the damage will be too severe to fix.

After being shot by the War Lords, the War Chief was barely able to survive. While being taken back to the War Lords' planet, his body attempted to regenerate. Due to the massive injuries and the lack of medical care, this regeneration aborted. The result was that he turned out looking like two individuals poorly fused together. (NA: Timewyrm: Exodus) The Doctor had one aborted regeneration when he was shot by a Dalek. In his tenth body The Doctor used the initial energy released by the regeneration process to heal himself then transferred excess energy into his dismembered hand. As a consequence he healed but did not change. After Donna touched the hand and it grew into a one hearted version of The Doctor, owing the "human biological metacrisis" her DNA caused.

Due to the fact this has never been seen before, and it is rare for a Time Lord to have a severed appendage, it is unknown if this used up a regeneration or not. .(DW: Journey's End)

Science
The exact mechanism that makes regeneration possible has not been stated, though many theories have been made. These varying explanations may or may not be compatible with each other.


 * One explanation was Cardinal Rassilon had been investigating a method of regenerating decaying and diseased tissue via a series of permanently carried self-replicating biogenic molecules. The cells of a Gallifreyan body can be repaired, restored and reorganised. This will result in a wholly new physical form. The brain cells would similarly be rearranged, though to a lesser degree, thus ensuring the new incarnation will replicate the memories and personality of the former incarnation. Cardinal Rassilon intended for this mechanism only to be used upon the Gallifreyan elite. He also input a parameter of 12 regenerative cycles to avoid decaying biogenic molecules. (BFA: Zagreus)


 * Another theory attributes regeneration to a "nanomolecular virus" that rebuilds the body much like the "self-replicating biogenic molecules". (EDA: The Gallifrey Chronicles)


 * A third theory is that Time Lords have triple-helix DNA: the third strand was added by Rassilon to make regeneration possible. (MA: The Crystal Bucephalus)


 * Another explanation is that regeneration may be linked to what is known as the "Rassilon Imprimatur", the symbiotic nuclei of a Time Lord that bonds him or her to a TARDIS, and allows his or her body to withstand the molecular stresses of time travel. (DW: The Two Doctors)


 * One partial explanation of the process links it to the release of massive amounts of a hormone known as lindos at moments of extreme trauma, with the hormone triggering the regeneration itself. Recently-regenerated Time Lords can be identified by the raised levels of lindos in their system. (DWN: The Twin Dilemma, BFA: Unregenerate!)

Side-Effects

 * Multiple Doctor stories such as DW: The Three Doctors and DW: The Five Doctors seem to indicate that with regeneration comes some degree of memory loss as the First Doctor is always shown to be much more wiser, intelligent, and familiar with himself than his future incarnations. These stories also suggest that the original incarnation of a Time Lord holds absolute authority over future incarnations.


 * Regenerations can cause radical changes in personalities when the catalyst is a mortal injury or otherwise forced regeneration.


 * The Doctor's most recent regenerations as well as the Master's seem to indicate that the energy expelled from a properly executed regeneration can cause harm to anyone within close range of a Time Lord. When the Doctor prepares to regenerate into his tenth incarnation he warns Rose Tyler to stand back. (DW: The Parting of the Ways) Jack Harkness gives the same warning to Donna Noble and Rose when the Doctor begins a tenth regeneration. (DW: The Stolen Earth) What manner of harm can befall anyone who makes contact with a Time Lord during regeneration is unknown. There have been several occasions where the Doctor has regenerated in close proximity to others (DW: The Tenth Planet, Planet of the Spiders, Logopolis) with no apparent ill effects to the onlookers. It's possible the explosion of energy during regeneration might be a consequence of Gallifrey, the Time Lords, and the Eye of Harmony no longer existing, as the only regenerations seen to date to be of this nature have occurred after the Last Great Time War.


 * After a regeneration is completed Time Lords become disorientated as they adjust to their new body and in some cases their new personality.


 * One side-effect of regeneration is the fact that different versions of the same Time Lord can encounter each other without causing a catastrophic effect. In Mawdryn Undead, two versions of the Brigadier touched, resulting in a massive temporal explosion. However, different incarnations of the Doctor have encountered each other on many occasions without causing the same effect when touching. The only noticeable side-effect of two different versions of the Doctor meeting each other has been the shorting out of the time differential, which caused the Fifth Doctor to age considerably when he met his Tenth incarnation in Time Crash. Another possible effect is a form of selective amnesia regarding the encounter, as future Doctors generally do not have recollections of past adventures with their previous incarnations. In the episodes The Two Doctors, The Three Doctors, and The Five Doctors, the later incarnations do not appear to remember the adventure, even though they would have experienced it multiple times from the perspective of their younger selves. In Time Crash, the Tenth Doctor recalls experiencing the adventure as the Fifth Doctor, but his memory is far from perfect, as he does not recall much of their conversation together. He is taken by surprise by the Fifth Doctor's referring to him as a fan, for example.

The Doctor's Regenerations
Following is a list of how each Doctor has regenerated, thus far.


 * 1) First Doctor: apparently succumbs to old age and/or possibly from the energy draining effects of the planet Mondas (DW: The Tenth Planet)
 * 2) Second Doctor: a forced regeneration and exile to Earth by the Time Lords. (DW: The War Games)
 * 3) Third Doctor: radiation poisoning from the Great One's cave of crystals on Metebelis III. (DW: Planet of the Spiders)
 * 4) Fourth Doctor: falls from the Pharos Project radio telescope. (DW: Logopolis)
 * 5) Fifth Doctor: spectrox toxaemia. (DW: The Caves of Androzani)
 * 6) Sixth Doctor: injured as the Rani attacks the Doctor's TARDIS (DW: Time and the Rani)
 * 7) Seventh Doctor: dies on the operating table while undergoing surgery for gunshot wounds. (DW: Doctor Who: The TV Movie)
 * 8) Eighth Doctor: unknown as of yet, possibly as a result of the Last Great Time War.
 * 9) Ninth Doctor: cellular degeneration caused by absorbing the energies of the time vortex from Rose Tyler, which she in turn had absorbed from the heart of the TARDIS. (DW: The Parting of the Ways)
 * 10) Tenth Doctor: Begins regeneration soon after being hit by Dalek fire, (DW: The Stolen Earth) aborted by redirecting the energy to his severed hand {DW: Journey's End)


 * The Eighth Doctor unofficially regenerated into the Alternative Ninth Doctor; the circumstances of this are not revealed. An unofficial regeneration from the Third Doctor into an alternate Fourth Doctor was also depicted, again with the cause unrevealed (Doctor Who and the Daleks in the Seven Keys to Doomsday).

Behind the Scenes
Regeneration was first introduced when the First Doctor (William Hartnell) changed into the Second Doctor (Patrick Troughton) in the closing moments of The Tenth Planet. Tradition has it that Hartnell himself thought up the idea of the Doctor being able to change into a new body as a means of keeping the series going after his departure. In The Power of the Daleks (the first story featuring the Second Doctor), the Doctor described himself as having been "renewed", and also said that the change was "part of the TARDIS."

The change in the Doctor's appearance was meant to occur several stories earlier, during The Celestial Toymaker, with the Toymaker capriciously changing the Doctor's appearance out of spite (the Doctor is invisible for most of the story and would have reappeared in the final episode played by a different actor). The reason for the change of plan is unknown - either it was decided to retain Hartnell in the role for a few more stories, or the actor was accidentally issued with a new contract by mistake, making it impossible to recast the Doctor at that moment in time.

The process was not actually referred to as "regeneration" until the end of Planet of the Spiders, when the Third Doctor (Jon Pertwee) changed into the Fourth (Tom Baker). Prior to this, the Doctor was simply described as having "changed his appearance."