Biodata contained information on a person's history and timeline (like temporal DNA). If you could manipulate a person's biodata you could alter their entire time stream. (PROSE: Alien Bodies)
On Gallifrey there were stores of all Time Lord biodata in the form of biodata extract. Excitonics was the technology underlying its circuitry. The Master was able to gain access to the Fourth Doctor's biodata extract to summon him to Gallifrey. (TV: The Deadly Assassin)
Omega used the biodata of the Fifth Doctor in an attempt to escape the Anti-matter universe. (TV: Arc of Infinity)
Faction Paradox used biodata in their rituals. They used a biodata extractor to take biodata from a subject, though blood would work, since it contained biodata. (PROSE: Alien Bodies)
A Little Brother of Faction Paradox altered the Eighth Doctor's biodata to change his origins and to remove his ability to perceive the colour violet. The Doctor later fixed this change. (PROSE: Unnatural History)
Compassion evolved into a TARDIS after a receiver given to her by the Doctor warped her biodata by processing signals from the TARDIS as Block Transfer Computations that altered her physiology. (PROSE: The Shadows of Avalon)
The Faction had developed biodata viruses that could infect potential Faction members to convert them to share the Faction's beliefs and abilities. Normally these viruses were too strong to infect Time Lords, but the virus was able to infect the Third Doctor when his history was changed and he was killed on Dust, resulting in him regenerating ahead of schedule. (PROSE: Interference - Book Two) Fortunately, the Doctor's TARDIS detected the change in the timeline and took the virus into itself, protecting the Doctor from its influence and allowing him to eventually erase the timeline where he had been infected and died on Dust. (PROSE: The Ancestor Cell)
Braxiatel had a Biodata Archive, with the biodata of every Time Lord in every regeneration, so that Gallifrey could be rebuilt should it fall to the Dogma Virus. (AUDIO: Panacea)