Cloning is a frequent theme in science-fiction and horror films. A clone replaces someone, unbeknownst to their family, or an army of clones plots to take over the universe.

But there’s a lot more to cloning — it’s a scientific pursuit that potentially has less maniacal applications, like creating organs to be transplanted into sick people and bringing extinct species back to life. Here’s what you need to know at your next trivia night.

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Twins are … clones?

According to the U.S. National Human Genome Research Institute, identical human twins are just one example of naturally occurring clones. They have almost the same DNA, because they develop when one fertilized egg splits into two — they are clones of one another. Other examples of clones in nature are creatures that reproduce asexually, without a partner, and thus produce offspring that is genetically identical.

The dinosaurs will probably stay dead

Even though cloning’s possible uses include bringing extinct animals back from the dead — referred to as de-extinction or resurrection biology — Encyclopaedia Britannica says the dinosaurs are not on the shortlist. “The extreme old age of specimens and the severe degradation of DNA over time” would make the task unlikely. Woolly mammoths, however, are a different story.

Not all clones are the same

Having the same genes is not enough to make things identical in every other way. “The environment also plays a big role in how an organism turns out,” the Human Genome Research Institute says. For example, it affects which of our genes display themselves and which don’t, turning them “on” and “off.”

Bender, Bender, Bender! Bender, Bender, Bender! Credit: Futurama

There are different kinds

Reproducing a new animal out of the genetic material of another is a type of biological cloning called reproductive cloning, but there is also gene cloning, which involves just copying pieces of DNA, the U.S. National Library of Medicine says. And therapeutic cloning uses genetic material to make stem cells that can be grown into different types of tissue, “to replace injured or diseased tissues in the human body.”

Physics also has its own brand of theoretical cloning, called the "no cloning theorem," and MinutePhysics explains why that process — which goes all the way down even to the spin of every particle — is impossible.

See also:

Eat Your Way Through the Periodic Table

A Genetically Engineered Virus Will Wipe Out Humanity