Have students view portions of the movie Jurassic Park. Ask them to comment on the feasibility of removing DNA from the fossils of extinct creatures, as was done in the movie, and recreate those creatures now. (This information is discussed within the first 45 minutes of the movie.) What sort of problems might a scientist encounter?
In the movie, dinosaur DNA was extracted from the belly of a mosquito-like creature embalmed in amber. The mosquito had extracted blood from the dinosaur, which was then preserved inside the mosquito. The dinosaur DNA was manipulated and used to reconstruct a dinosaur, which then hatched from its egg.
Using the interactive CD-ROM exercise suggested in the text in Figure 8.16, students can view DNA evidence and see how it can be used to solve crimes.
DNA fingerprinting employs small bits of semen, hair, nails, skin, or blood taken from a crime scene or a victim of a crime. The DNA is isolated from these samples, and a restiction enzyme is employed to cut repetitive portions of DNA into portions of varying length. How long the restriction fragments happen to be is unique to each person. The fragments are then sorted according to length using gel electrophoresis--small fragments migrate further. A membrane is used to blot the electrophoresis gel and pick up a print of the gel. Radioactively labelled DNA probes are then used to mark certain sequences of nucleotides within the suspects' DNA. The membrane is then used to expose X-ray film, and a DNA fingerprint with a unique series of banding patterns is the result. No two people have the same banding patterns, with the exception of identical twins. The probability that two people chosen at random have the same banding pattern is on the order of one in a billion. DNA fingerprinting is a very precise method of identification.