The original Jurassic Park film reveals that frog DNA was used to help create the dinosaurs, causing a problem with InGen's plan to limit breeding. Released in 1993, Steven Spielberg's classic not only boasted ground-breaking advancements in CGI technology, but it also explored the scientific phenomena of cloning. While the logistics are not fully explained in the movie, they still provide a compelling look into the reemergence of dinosaurs.

When paleontologist Dr. Alan Grant and the team first arrive at the Jurassic Park Visitor Center, they are treated to a tour by John Hammond, founder of the park and of InGen, the company which makes dinosaur cloning possible. Their first stop includes a film narrated by Mr. DNA, the animated helix, who explains how the dinosaurs came to be. In simplified terms, scientists were able to extract dinosaur blood from prehistoric mosquitos preserved in amber. Because most of the samples' genomes were incomplete, geneticists needed something to, as Mr. DNA says, "fill in the holes and complete the code." This is where frog DNA came in.

Related: Jurassic Park: All 6 Dinosaurs That Appear In The First Movie Explained

Frog DNA serves as both an easy, uncomplicated solution to the dinosaurs' genetic sequence and a plot device for later on in the film. It's that DNA solution that is responsible for every dinosaur in the Jurassic Park series, like the T-Rex and Velociraptor before the later movies move into more overt genetic splicing. It's combined with the dinosaurs' DNA sequence to make a finalized version for fertilization, filling in the gaps from degradation over the thousands of years since their extinction. In the film, it's only frog DNA that was used to serve the plot and explain how some dinosaurs have been able to change sex, while the original book uses a number of additional options. Fundamentally, it serves two other purposes too. Not only does it foreshadow the franchise's genetic tinkering and establishes that Dr Henry Wu's morals come second to his scientific drive, while adding an accessible means to explain how the amber extraction method can possibly lead to full sequence DNA cloning.

Mr DNA Jurassic Park

Michael Crichton's novel, on which the movie is based, provides a complex analysis of the different chicken and amphibian genomes used in creating and boosting the growth of dinosaurs. Jurassic Park's filmmakers likely wanted to make the process as simple as possible for audiences to understand, so frog DNA became the sole additional insertion into the dinosaurs' biological makeup. Frog DNA is mentioned again in a later scene, when Dr. Grant, Lex, and Tim, discover freshly-hatched eggs outside of the lab. According to Dr. Wu, the head geneticist of the park's lab, all dinosaurs are programmed to be female, so breeding should be impossible. Upon finding the eggs, Dr. Grant remarks that some West African frogs can alter their sex in a single-sex space. By marrying a frog’s genetic code with the dinosaurs', scientists gave dinosaurs the frog’s ability to change sex and, therefore, mate. However, what type of frog DNA was actually used and whether the scientists knew about this trait from their research remains unclear.

Though frog DNA is touched upon only twice in Jurassic Park, it is an essential part of the film's plot and the science behind making dinosaurs. The stakes are even higher knowing that dinosaurs and their natural-born children are running rampant around the island. Frog DNA is also a stepping stone for completely man-made dinosaur hybrids like the Indominus Rex to wreak havoc in Jurassic World and its sequels.

Next: Jurassic World 3: Every Way Dominion Is Different To All Previous Movies

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