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 (and a few other life-forms) could renew themselves physically by changing themselves if worn out by age or has suffered some life-threatening injury or infection or even at will.

The regeneration
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) During the first few hours of the regeneration, the Time Lord will often suffer from confusion, erratic behaviour and memory loss. (DW: Castrovalva, The Twin Dilemma, The Christmas Invasion) 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) After his regeneration, the Doctor implied that his TARDIS helped the process along. (DW: The Power of the Daleks) Some Time Lords, however, may regenerate with little or no overt complications, for example, Romana. (DW: Destiny of the Daleks)

Just prior to his ninth regeneration, the Doctor warned his companions to keep away from him. (During a partial regeneration which occurred during the Doctor's partial tenth regeneration, Jack did this.) This would seem to imply that the energy released during the process posed some level of danger to Humans, and possibly that them being too close may pose a danger to the Time Lord. (DW: The Parting of the Ways, The Stolen Earth) However at least one regeneration occurred with other individuals seen in close proximity (DW: Logopolis).

Limitations
Though Time Lords can regenerate after severe injuries, regeneration does not seem to be guaranteed. 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), although it is possible he meant the particular incarnation, and there have been numerous occasions in his lifetimes where survival -- including regeneration -- was not assured. A very sudden death may also make it impossible to regenerate. (DW: Turn Left) As well, the interference of some medications, such as anaesthesia, may disrupt or destroy the regenerative process. (DW: Doctor Who: The TV Movie)

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, was offered "regeneration: a whole new life cycle" as an incentive to rescue the four Doctors from the Death Zone. (DW: The Five Doctors)

Post-regenerative effects
Most or all memories persist after regenerations. The Doctor, in particular, though not so much other Time Lords have exhibited mood swings and confusion. It took some time for the regeneration fifth incarnation to remember his own identity. (DW: Castrovalva) On one occasion, he attempted to strangle Peri to death before re-asserting control of himself (DW: The Twin Dilemma) and on another he almost crashed the TARDIS (DW: Children in Need Special) A Zero Room can help with this. (DW: Castrovalva)

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, (DW: Destiny of the Daleks) while Azmael initiated a thirteenth regeneration in order to end his life (DW: The Twin Dilemma).

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) Although it is possible this was merely a coincidence, as most regenerations result in a physically younger form. 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 criticized Romana for taking on the form of another person, suggesting such things were not unheard of (DW: Destiny of the Daleks). In contrast to Romana, the Doctor did 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), and would restate this immediately prior to his ninth regeneration (DW: The Parting of the Ways).

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. The process can also be stopped with some difficulty, as the Master did in order to spite the Doctor so he died of a gunshot wound (DW: Last of the Time Lords).

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)

Meta-Crisis
A Time Lord can prevent death and regeneration by focusing the regenerative energies into a severed appendage. The severed appendage siphons off the excess energy while the Time Lord uses just enough of it to heal wounds. This results in the appendage storing enough energy to actually grow a nearly identical Time Lord if it comes in contact with living tissue. As a consequence he healed but did not change. After Donna touched the hand, it grew into a one hearted version of The Doctor, owing the "human biological metacrisis" her DNA caused. (DW: Journey's End)


 * 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.

Scientific explanation
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 that 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 could be repaired, restored and reorganised. This would 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. Rassilon intended for this mechanism only to be used upon the Gallifreyan elite. He also inputted 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)


 * 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!)

The regenerative cycle
The Time Lords had a limited regenerative cycle of twelve incarnations, after which they had no more incarnations. (DW: The Deadly Assassin, Doctor Who: The TV Movie) Other life forms, for example the Minyans could have hundreds. As noted above, Rassilon apparently had physical reasons to impose this restriction. (BFA: Zagreus) The High Council, offered the Master a new regenerative cycle if he complied with rescuing the various incarnation of the Doctor from the Death Zone. (DW: The Five Doctors)

The crew of the Minyans' ship the P7E, however, had had about a thousand regenerations, by which time, however, they wearied of life. (DW: Underworld) Mawdryn and his followers, who had stolen the Time Lords' regeneration technology, also had an apparently limitless number of incarnations, though they had non control over when they would happen to into which form, often grotesque, they would have change into. Consequently, they also longed for death, making their mutations of a kind of de factor punishment by the Time Lords for stealing their technology. (DW: Mawdryn Undead)

The Doctor

 * Apparently succumbs to old age and/or fatigue (DW: The Tenth Planet)
 * A forced regeneration and exile to Earth by the Time Lords. (DW: The War Games)
 * Radiation poisoning from the Great One's cave of crystals on Metebelis III. (DW: Planet of the Spiders)
 * Falls from the Pharos Project radio telescope. (DW: Logopolis)
 * Spectrox toxaemia exposure. (DW: The Caves of Androzani)
 * Injured as the Rani attacks the Doctor's TARDIS (DW: Time and the Rani)
 * Died on the operating table while undergoing exploratory heart surgery by Dr. Grace Holloway. (DW: Doctor Who: The TV Movie)
 * Unknown; implied to have taken place recently. (Prior to Rose)
 * 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)
 * Partial regeneration after being hit by Dalek fire, (DW: The Stolen Earth); aborted by redirecting the energy to his severed hand (DW: Journey's End)

The Master

 * Uses up most of his regenerations escaping from the Darkheart (MA: The Dark Path)
 * Uses up his regenerations, up until his last, recovering from bomb blast set by Susan Foreman (EDA: Legacy of the Daleks)
 * These accounts contradict each other somewhat.


 * Utilizes the power of the Source to steal the body of Tremas (DW: The Keeper of Traken)
 * Steals the body of the Human Bruce (DW: Doctor Who: The TV Movie)
 * Regenerates to survive wound from gun fired by Chantho (DW: Utopia)


 * The Master had gotten resurrected to fight the Last Great Time War at this point, and probably had a new regenerative cycle.

Romana

 * Regenerated into duplicate body to Princess Astra. (DW: Destiny of the Daleks)
 * Regenerated into an incarnation more suited to fighting the War with the Enemy. (EDA: Shadows of Avalon)

Rassilon
Rassilon was 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)

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 next story, the Doctor described himself as having been "renewed", and also said that the change was "part of the TARDIS." Orginally, the Production team meant for the Doctor to have used the TARDIS to reverse time and "rejuvenate" himself, though they may have abandoned this explanation by the time Patrick Troughton took over.

The change in the Doctor's appearance was meant to occur several stories earlier, during The Celestial Toymaker, with the Toymaker capriciously having changed the Doctor's appearance out of spite. (The Doctor is invisible and unable to speak for most of the story anyway.) 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. (A plot device similar to this would occur in The Mind Robber to cover Frazer Hines' temporary replacement by his cousin, Hamish Wilson, after Hines contracted an illness.)


 * 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."