Mitosis was the process by which a eukaryotic cell separated the chromosomes in its cell nucleus into two identical sets.
A magnetic organism encountered by the USS Enterprise in 2269 was able to reproduce itself by mitosis and take over the control systems of starships, computer centers, even planets. (TAS: "Beyond the Farthest Star")
In 2369, Dr. Beverly Crusher asked Amanda Rogers to record the rate of mitosis in live bacilli samples. Rogers artificially inflated the process using her Q powers, rendering the experiment useless. (TNG: "True Q")
Later that year, embryonic quantum singularity lifeforms were discovered in a state of mitosis in the engine core of a Romulan warbird. (TNG: "Timescape")
By 2371, Sulan had developed a procedure to stimulate cell division as a kind of enhanced mitosis. (VOY: "Faces")
Also that year, Julian Bashir discovered that an Jem'Hadar youth's cellular mitosis had been artificially enhanced. (DS9: "The Abandoned")
In 2372, when hyper-evolution caused Tom Paris' cells to undergo mitosis, The Doctor used a bio-suppressor field to inhibit the process. (VOY: "Threshold")