Gattaca is the name of a space agency in the not-too-distant future, where the preparation for man's first journey to Saturn's moon, Titan, is in progress. Among the people vying to leave Earth and explore Titan is someone who goes by the name of Jerome Morrow (Ethan Hawke). Morrow is fully qualified for this job: he has the right genetic material that puts him a cut above all the rest in terms of mental and physical skills.
The catch is that Jerome Morrow is really Vincent Freeman, an "in-valid" with defective genes, who has managed to infiltrate the elite space agency by faking his identity---right down to the nucleic acid level. Vincent routinely obtains blood, hair, and urine samples from the real Jerome Morrow (Jude Law) to pass identification and screening tests. The real Morrow is not able to realise his potential since he was crippled in an accident, and therefore needs Vincent as much as Vincent needs him.
Throw in some sibling rivalry between Vincent and his "valid" brother, a murder sub-plot, and a love interest for Vincent, you end up with Gattaca. The story is essentially about how Vincent overcomes the programming in his in-valid genes and competes against the best in the "valid" world.
The scientific premise, like in most science-fiction movies, combines a mix of truth and fiction. In the movie, the alleles from parents are so chosen that the combination produces the optimal arrangement in terms of the child's genotype. But we know enough right now to realise that even in situations where there is a great degree of genetic predisposition, it is quite probable that that predisposition (positive or negative) is never realised. For more complex behavioural traits such as intelligence, aptitude test results would be a far better indicator than genetic makeup. In other words, any correlation people may find between a complex behavioural trait such as intelligence and genetics is for all practical purposes controlled by the environment, given the "edge of chaos" nature of such traits.
What is disturbing about our genetic engineering capabilities today is no more disturbing than our medical engineering capabilities (and there are plenty of disturbing ramifications). The genetic component simply provides one additional way to discriminate in the real world, just as it is routinely done with age, sex, years of experience, education, and physical ability: Consider the physical and mental requirements for being an astronaut today, or even for admission to college. Information, of any sort, is a valuable commodity in this day and age, and the kind encoded in DNA is no exception. Humans naturally use information to discriminate. I would argue that for some of scenarios posited in Gattaca, the genetic information is far less reliable than physiological and psychological histories.
The acting by all the characters is quite good, though Jude Law as the real Jerome Morrow manages to steal the show. The narrative style at the beginning of the movie I thought was far more interesting than the actual sequences toward the end. Definitely worth watching on the big screen.