Jurassic Park was a cautionary tale about genetic manipulation. Could that actually happen? Why or why not?

(The fourth of five questions I may be asked tomorrow as part of a panel on DNA and
ethics.)

I’ve only seen the first two movies, so I can’t really comment on the technical details as presented in the books (where I imagine they are presented in more detail). I hope I don’t get asked this question. But a few minutes with Google yields the following:

• According to the BBC, a grove of plants that are survivors from the Jurassic age was found in Australia about 10 years ago, and cuttings from those plants will be marketed to gardners in 2005. But those plants weren’t re-constructed — they simply happened to survive all that time.
• Dolly the sheep was in fact cloned from a parent, but she started off as a living cell. And she was recently put to sleep because she aged prematurely — suggesting that science has to progress a lot further to make a successful cloning even with live tissue.
• IN 2002, Japanese scientists announced a plan to clone a mammoth from frozen tissue samples. Somebody thinks this is possible, or they wouldn’t be trying it. But the mammoth sample is about 25,000 years old. Success with a 25,000 year-old mammoth wouldn’t necessarily indicate progress towards cloning an animal extinct for 65-million-years.
• I gather that fossilization is a lot more destructive than freezing. I don’t know much about the digestion of prehistoric mosquitos, but I don’t imagine that being in the stomach of an insect would be the best environment to preserve a blood sample.