Genetic engineering

Genetic engineering was the process of modifying an organism by changing their DNA. It was closely related to the concept of mutation.

The Daleks
The Daleks had done extensive engineering to themselves and others. They had originally started as modified Kaleds. (TV: Genesis of the Daleks) Civil wars were known to be fought over genetic purity (TV: The Evil of the Daleks) and some Dalek technology, like the Progenitor, wouldn't recognise impure Daleks. (TV: Victory of the Daleks)

At one point, the Daleks searched for the Human Factor and the Dalek Factor, traits that distinguished humans and Daleks from other species. By implanting the Human Factor into Alpha, Beta, Omega and other Daleks, humanised Daleks were created. This led to the Great Civil War as the humanised Daleks questioned and rebelled against the Daleks' orders. The opposite procedure occurred when the Daleks implanted the Dalek Factor into Theodore Maxtible. (TV: The Evil of the Daleks) The Dalek Factor turned humans into Dalek servants and in some cases when they were mortally injured, they initiated a type of regeneration. (PROSE: I am a Dalek)

Daleks of human origin were created on several occasions, in two different instances by Davros and the Dalek Emperor. (TV: Revelation of the Daleks, The Parting of the Ways)

In 1930 New York City, the Cult of Skaro created two forms of Dalek-human hybrids. Dalek Sec became a human-Dalek after merging with Mr Diagoras, (TV: Daleks in Manhattan) and an army of hybrids were created by Dalek DNA implanted into near-dead humans with their minds wiped; these were also given Time Lord DNA after an attempt by the Tenth Doctor to destroy the transmitter on the top of the Empire State Building which powered their creation. He was struck by lightning, fusing his DNA into their genetic code. This made them question the Daleks' orders. (TV: Evolution of the Daleks) While in 1930 New York the Cult of Skaro implanted animal DNA into humans, turning them into pig slaves. (TV: Daleks in Manhattan)

Other species
The Tzun integrated the DNA of other species into their own. (PROSE: First Frontier)

The Yend attempted to modify themselves, but the radiation of the star Mortain caused uncontrollable mutations. (PROSE: The Sons of the Crab)

The Jadean were genetically engineered to withstand telepathic readings. (PROSE: Placebo Effect)

Some Rakweed were genetically modified by Tree Slitheen-Blathereen to grow faster. (TV: The Gift)

The Korven implanted Meron DNA in their ally, Thorne, effectively turning him into one. (TV: The Eclipse of the Korven)

A Karfelon scientist known as Megelen, while experimenting with Morlox DNA, was accidentally fused with it and became the Borad. (TV: Timelash)

The Luminus cult combined the DNA of the Sline lizard and the Aaglon shark to create the Slaag. (PROSE: Tragedy Day)

Ravus Oldeman created the Bloodhunter by combining DNA samples collected from the surface of Akoshemon with human DNA and force generating the resulting life form, in an attempt to create a creature capable of autonomous self-stasis. (PROSE: Fear of the Dark)

The humanoid Dastari was considered a pioneer of genetic engineering by the Sixth Doctor. (TV: The Two Doctors)

Humans living on an alien planet genetically engineered native life forms to resemble dragons. (COMIC: The Dragon Lord)

The Silents were genetically engineered so that one would forget them after looking away. (TV: The Time of the Doctor)

Other references
Marunianism was opposed to genetic engineering. (PROSE: Dry Pilgrimage)