Even when there is a twin clone of a clone, Orphan Black gets its science right.

The second season of the wildly popular Orphan Black series will be coming to another dramatic close this Saturday. Like the last, this season has been filled with ethical and philosophical intrigue centered on clones, evil corporations, and human genetics. For how fantastical this premise could be, Orphan Black pushes today’s science far enough into the future to be fascinating while being conservative enough to be educational. In fact, you’ll learn more about human genetics from the show than just about anywhere else on television.

So what is a clone anyway?

Very basically, a clone is an organism that has the exact same genetic material as the parent organism from which the clone was created. Your clone would have the same DNA as you. Creating a clone isn’t all science fiction either—it’s how some animals reproduce. For example, a few species of jellyfish have a larval stage of their lives where all they do is bud off clones of themselves. The largest organism on earth, a colony of quaking aspen trees called “Pando,” is made up of thousands and thousands of interconnected clones. Indeed, any animal that reproduces asexually is a clone factory like the Dyad Institute.

Humans obviously don’t reproduce asexually, so we have to clone organisms the hard way. To make a Sarah Manning from whomever the original was, you first need a donor egg. After removing the nucleus from the egg, scientists would then fuse another cell’s nucleus from the organism they wish to clone into the empty egg (with a tiny jolt of electricity). The now complete egg is then inserted into a surrogate womb and hopefully the eggs starts to divide. If the embryo comes to term, a clone is born. (You can find a great history of cloning, along with an explanation of all the different cloning processes here.)

Because of the immense controversy surrounding human cloning, you aren’t likely to see a Cosima Niehaus or Alison Hendrix running around anytime soon. But there certainly are human clones among us. It has nothing to do with genetic engineering—identical twins are clones for all intents and purposes.

The only real difference between clones and identical twins is the process that creates them. Both identical twins and clones share the same genetic material, but identical twins come from a natural splitting of a fertilized egg inside a womb. So when Helena looks at Sarah, she sees a clone of a clone. But even though identical twins are the natural equivalent of human clones, that doesn’t mean there aren’t small differences. Identical twins are actually more similar to each other than to another clone of the same “original.”

Identical twins have the benefit of developing at nearly the same time in the same environment and being born to the same parents (usually). This reduces the number of variables that can creep into a child’s development. Everything from a mother’s microbial makeup to the environment a child is born into can affect the way that child’s genes are expressed, clone or not. DNA doesn’t copy perfectly during development, imprinting different mutations between clones and between identical twins. And when a cell from an organism to be cloned is inserted into a donor egg, the reprogramming that occurs at a genetic level also leaves its stamp on the clone that will differ slightly from the original. In short, clones and identical twins are defined by their genetic similarity, but the similarity is never 100 percent thanks to these creeping variables.

Orphan Black gets most of this right. The show makes a great point about how nature as well as nurture steer human development by having Tatiana Maslany play clones with very different dispositions and personalities. By acknowledging that genes are not destiny, Orphan Black displays the nuance of what we know scientifically about clones, twins, and development quite well. (However, one thing the show gets wrong is that neither clones nor identical twins would have identical fingerprints. That’s a truism that doesn’t play out in the real world. Sorry aspiring identical twin criminals.)

One of the more intriguing genetic anomalies that Orphan Black gets right is the odd case of “mirror-image” twins. When a fertilized egg splits off into two at a later stage in embryonic timing than normal, there’s a chance that once the twins are born, one will have reversed symmetry. Handedness could flip, as could dental structure or even organ placement. Called situs inversus, the flipping of organ placement to the other side of the body is what Helena has with respect to her mirror-image twin Sarah. Imagine Sarah and Helena looking right at each other. If Sarah placed her right hand over her heart and Helena placed her left, it would look like it would in a mirror. But stand them side-by-side and their hands would be on different sides of their chests.

Beyond the complications of genetics and cloning and reversed organs, maybe the most basic thing that Orphan Black gets right is why researchers are so interested in clones in the first place—clones could tell us how genes really affect human life. But for the moment, human cloning is too controversial to create a research paradigm for. Scientists today settle for the natural equivalent—identical twins—to tease out the great development debate: are we more influenced by nature or nurture?

Twins are one of nature’s great experiments. They are born with the same genes but different environments. Without subjecting anyone to unethical conditions, scientists can simply track the lives of twins to uncover just how much genetics factor into the course of their (and by extension our) lives. For example, by tracking twins we know that some human attributes are largely genetic. If one identical twin is tall, it’s almost a certainty that the other twin will also be tall. The same is true for some diseases. If one twin develops Alzheimer’s, there is a very good chance the other will as well. But for most things we track twins for, there is a lot of unexplained variance between them. In other words, genetics isn’t everything.

Being able to ethically produce human clones, and study them without incident, would be a tremendous boon for science. Think of the diseases we could pin down genetically or the environmental influences we could regulate or promote. Of course, it would be a lot easier to do all of this unethically, which is the whole reason why the Dyad Institute made the clones in the first place.

Even if we could mass-produce clones for research, who would own them? Would they belong to the corporation or hospital or to themselves as people? Orphan Black handles this philosophical tension beautifully, even delving into some of the politics on patenting human genes. Luckily, in the real world, the girls would have the law on their side.

Last June, the United States Supreme Court determined that naturally occurring sequences of the human genome could not be patented. Myriad Genetics Inc. claimed in the case that because their discovery of the BRAC1 and BRCA2 genes—the genes that we now know are huge factors in the development of breast cancer—was like finding a genetic needle in a haystack among our 20,000 human genes, the company should be able to patent them. (Discovering mutations in these genes is what led Angelina Jolie to undergo a double-mastectomy.) The court ruled unanimously against Myriad, stating that no one can patent what already existed in nature.

In the episode “Endless Forms Most Beautiful” (a reference to a concluding quote in Charles Darwin’s Origin of Species), Cosima is able to decipher the clones’ genetic code and discover a message written in nucleotides: “This organism and derivative genetic material is restricted intellectual property.” The message constitutes Dyad’s patent. What it implies is that Dyad has patented a modified sequence of DNA already found in the clones’ genome. If this is the case, Dyad’s patent would never hold up in our courts, and the women would have real freedom. However, it could be the case that Dyad created the entire clone genome synthetically, a process which would be patentable, and really would cause ethical and existential problems for the girls. In this scenario, Cosima wouldn’t even be able to study her own genome without infringing on Dyad’s rights.

But on the issue of what exactly is residing inside the clones’ genome, Orphan Black remains mysterious. That’s intentional. Speaking with Think Progress, the show’s science advisor Cosima Herter (the inspiration for the character of the same name) was quoted as saying:

“We’re raising those questions in really provocative ways. [The show] is not about giving you the answers. I don’t think anybody has them. It’s about who has the right to ask those questions and who regulates how they get answered. So it’s about agency on all these different kinds of levels.”

Gene patenting, nature vs. nurture, ideas of the self…these are inherently messy issues that we should struggle with; that we are struggling with. The brilliance of Orphan Black is that it acknowledges this nuance. It doesn’t make each clone an identical replica in speech, dress, appearance or preference. Neither does it make the clones bizzaro opposites of each other or reduce a tormented personality to something one-dimensional. Orphan Black is complicated and murky, illuminating and fascinating, making it closer to actual science than just about any other show on television.

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Kyle Hill is the Chief Science Officer of the Nerdist enterprise. Follow the geekery on Twitter @Sci_Phile.

IMAGES: BBC America