I didn't like the movie at all - I went to the movies to see it when it first came out, but the storyline was patchy and I thought it was pretty boring really. It presented a fictional view on human cloning - the nucleus from cells taken from the first borns body (after he was hit by a car and killed) was used to transfect one of the mothers oocytes (eggs). Once this had formed a foetus, it was essentially a clone of the first born - the exact same DNA. Somehow, the first borns thoughts and memories were also transferred to Zack in the process (meaning that all of your thoughts and memories are stored on your DNA, not just your physical features or personality characteristics as currently thought). Instead of living his own life, poor old Zack was living the life of his dead projenator (the first born).
Some people I have talked to after watching the movie suggested that this might be possible. Ofcourse, their realm is the esoteric and not the scientific, and just the thought of people believing in the possiblity of thoughts and memories being transferred in DNA is scary.
Ever thought about the different possible title? GOD SEND.... or GODS END? (once we have mastered the ability to clone people and create life on our own, why do we need god?). Something to think about... If you haven't seen the movie though, I wouldn't waste your time.