One of the hallmarks of the steampunk aesthetic is the Mad Scientist. There are two kinds of folks who fall into this category -- engineers who build fantastic machinery and physical scientists who work with the organic side of things. Examples of both are Doctor Loveless from Wild Wild West and Doctor Victor Frankstein from the eponymous novel.
Doctor Frankenstein works in what's called "natural philosophy" (another term for the blend of chemistry, biology, and medicine that existed before science became compartmentalized). His story focuses the proto-steampunk aesthetic of Frankenstein on the science behind reanimating dead flesh. More often than not, we see something like this in horror movies rather than in science fiction. However, and this is a fairly big "however," the biological sciences lend themselves very easily to steampunk when set in the right time frame.
Gail Carriger's Soulless, which I've blogged on before, includes a cabal (I love that word) of mad scientists who are trying to craft supernatural creatures by using blood transference. They expect that doing so will allow them to understand the supernatural enough to destroy it. This story's timeframe is the 1850s, a fact Carriger is well aware of, and thus she gives the scientists just enough knowledge to sound like academics of the period.
Scott Westerfield, on the other hand, admits that Leviathan assumes that genetics and DNA were discovered decades before their actual point in scientific history. That's the only way certain bits of his technology can work. If, however, you accept this, then the scientists still need to not have the same benefits that an early 21st Century geneticist would. It's hard to manage, but worthwhile in order to craft an effective view of the world.
The engineer-type mad scientist is exampled by Doctor Loveless of Wild Wild West. This is the Will Smith/Kenneth Branagh* version I'm talking about, by the way. In that movie, Doctor Loveless creates a steam-powered mechanical spider that evokes images of Godzilla and the great (bad) monster movies of decades before. He also has a mechanical wheelchair of his own devising, and augmented his soldiers with mechanical accouterments. His mad science exampled itself by the mechanical devices that he used in his villainy rather than any sort of fiddling with genetics.
The webcomic Girl Genius by Phil and Kaja Foglio deals with both kinds of Mad Science. When a character in their version of Europe (Europa) has the skill to craft fantastic machines or play Devil Went Down to Georgia on the fiddle of someone's genetic code, they're called Sparks. These "Sparks" have the possibility of flipping into Mad Scientist mode at any time. Sometimes this happens with hilarious results.
Anyway, my point is thus: Mad Science is a tried and true application of the steampunk worldview. In fact, one of the things you see a lot in the works that birthed the genre and the proto-steampunk novels is a sort of nod to the way technology can both go right and go horribly wrong. In this, steampunk shares its themes with general science fiction. But, if you add the science of the Victorians with the technology they had at their fingertips, well then you get a chance to play with some very entertaining insane people who happen to be really, really smart.
* I'll watch any Kenneth Branagh movie at least once. Say what you want about his commercial films -- very few actors can rock Shakespeare like he can.