Answer:
The correct answer to fill in the blank is: transformation.
Explanation:
Transformation is a process that happens to a) cells when they change their phenotypes due to new genetic material, or b) cultured cells that keep having spontaneous phenotypic alterations due to the changes in their DNA.
Transformation can occur because spontaneously, or because of an infection with a transforming virus, gene transfection, exposure to chemical carcinogens or exposure to ionizing radiations.