I've watched the Jurassic Park movies recently and I kind of got to wondering about some aspects of how the genetics is "supposed to work" in the movies compared to the real world.
For the sake of discussion we'll accept that it's conceivable and even plausible inGen was able to recover blood from prehistoric mosquitoes that were preserved in amber. Further allowing it was possible to take the recovered blood and use gene splicing to create dinosaurs. That's a LOT of hand waving we're giving them but it's all on some level "possible."
But here's some questions:
The first movie spends a lot of time going with the (now) popular theory that dinosaurs were more closely related to modern-day birds than reptiles. But when inGen created the Jurassic Park dinosaurs they spliced the recovered DNA with the DNA code of a frog in order to fill in the gaps in the degraded genetic code. Wouldn't this cause some problems? Splicing the DNA of a warm-blooded/bird-related animal with a cold-blooded reptilian animal? Wouldn't the result be anything BUT a dinosaur? Hell, wouldn't there be some pretty strong conflicts in the genetic code likely making a viable embryo unlikely? (Oddly enough in the background in that scene you can hear "Mr. DNA" tell the guests the zygote was implanted into a ostrich egg in order to mature.)
But, okay, the recovered dino-DNA needs to be spliced with something because over the millions of years its degraded and has holes. Why does it need to be spliced with anything? If a single drop of blood contains countless strands of DNA wouldn't it be possible to splice the DNA with itself? If we're to accept the geneticists were able to so easily fill in the gaps with the reptilian DNA then wouldn't be just as accepting that they could just scan multiple strands of DNA and piece together the gaps from other strands? Surely not all DNA strands are going degrade the exact same way.
And finally this is I think sort of the big one.
So the DNA between a dinosaur and a frog has been spliced together to create a "mostly-dinosaur-like" creature. (We'll assume that the reptilian DNA "worked better", took, and resulted in something that came out looking mostly like how we expect dinosaurs to look rather than the more bird-like looking things they likely actually were.) In the movie it's said that they bred all of the dinosaurs in Jurassic Park to be female in order to prevent breeding in the wild. I believe the book said they choose female because it was thought they'd be the tamer gender to go with in the movie (and probably also in the book) it's implied it's simply easier to deny an embryo the ability to become male since all embryos are inherently female anyway.
Of course in both the movie and the book "life finds a way" and the dinosaurs spontaneously change genders in the "wild" to produce offspring as some species of frog are known to do.
Here's the problem I see. The dinosaurs in Jurassic Park are hybrids! They're hybrids of dinosaurs and frogs. If I understand correctly hybrids are inherently sterile! (At least this is true when it comes to hybrid plants.) There should be no problems at all with breeding in Jurassic Park because all of their animals should naturally be born sterile. Sure, maybe, we can go with Malcolm's "life finds a way" theory with this and still breeding might happen, but almost as a rule hybrids can't breed. Nature pretty much doesn't accept hybrids because they're unnatural.
Hell, this is why bananas are fruits even though they don't contain seeds. Modern-day bananas have been selectively breed and spliced to create what we think of today as a banana. They don't have seeds because they're hybrids and are sterile. Same goes for most other seedless fruits. They're seedless because of genetic engineering by making hybrid plants.