So, consider this: we are given the toolbox of an infinite number of genes found in nature, a plasmid to carry any number of these genes, and Adam to differentiate into any cell or tissue imaginable. You create a thought out process that, despite being far from any reality, makes sense. Imagine how a plasmid like "electro bolt" could have actually worked by differentiating Adam into electrocytes (muscle-like cells found in electric eels) using genes from electric fish engineered into plasmids. On their own these cells create about 0.15 volts but in unison and acting at a high frequency electrocute and stun unsuspecting Splicers. Sounds silly?
Researchers are already keen on sequencing the genome of the electric eel to better understand how the animal already is capable of this.
Some plasmids would have easily unraveled in interesting ways to function biologically such as symbiotic relationships that allowed harboring and weaponizing bee swarms. However, other 'plasmids' were the result of giant leaps in logical steps to empower players with immolating fireballs, and freezing ice jets. I don't like splitting hairs on a would-be science fiction, but it should be noted that there is no shortage on the biological phenomena that could have offered players the same pleasures of setting people on fire or strategic escapes (teleportation) from danger.
Similarly, new game mechanics could have been introduced by known genes and functions from 50-year old science text books. Why not borrow the glow of firefly luciferase to introduce flashlight mechanics commonly found in the survival-horror genre? Imagine hearing Subject Delta/ Jack breathing in deeply to circulate the required oxygen to catalyze the activity of luciferase. After a few deep breaths, the character's fingertips start to glow green and slowly light up the poorly lit corners of Rapture.