Re: How about combining frog DNA and dinosaur DNA?

The short answer is no -- which is not to say that Crichton's idea of cloning dinosaurs is bad or that it would never work. In my opinion, this is an example of good "science fiction" where the "what's possible" science of today is extended and pushed to create another possibility. There is an excellent book written by Rob DeSalle and David Lindley called The Science of Jurassic Park and the Lost World that goes through the possibilities of cloning dinosaurs as in Crichton's book/film. It goes through each of the steps and tells you why cloning dinosuars can or cannot work.

There are lots of issues with Crichton's plan especially since we just don't know enough about the DNA that makes a dinosaur. Assuming that you can get blood from an amber-preserved mosquito -- there are lots of issues with that too -- which type of dinosaur did you get it from? What if it isn't a dinosaur? How can you tell? We have nothing to compare it too. Dinosaurs fit somewhere between reptiles and birds, but crocodile, frog, and chicken DNA are all quite different -- different in where it matters, the parts that make a frog a frog and not a chicken. Frogs, crocs and chickens all have different numbers of chromosomes. How would you know how many "the" dinosaur had? Then there's the problem with "building" a chromosome. It's one thing to "get" DNA and sequence it, but that doesn't mean you can inject it into an egg and assume that the DNA piece will be used. The DNA of an organism, its genome, is packaged into chromosomes. The packaging includes proteins that help wrap it up, and to prevent the DNA from being damaged, and other proteins that act as a scaffold to give it shape to fit in a nucleus but also to help control expression of the genes. (See animation of the process in DNA Interactive > Genome > Chromosome Closeup > 3D animation chromosome coiling.) "Naked" DNA as in a dinosaur DNA sequence patched with frog DNA would not have the packaging and would likely get degraded.

DeSalle and Lindley's book goes through a lot of other problems -- it's not just the dinosaurs you would have to clone, you'd have to reproduce all the plants/food as well, then there is the hatching problem. How do you incubate the developing dinosaur embryo? What do you use for an egg? The size and shape of the egg and the toughness of the shell has to be right in order for the embryo inside to grow properly -- that's the case for birds and reptiles.

I recommend reading DeSalle and Lindley's book. It's short and easy to read and can give you even more reasons why cloning dinosaurs can or cannot work.