1. Some diseases can occur through different genetic abnormalities. For example, there are two main types of colorectal cancer which can occur, one due to mutations in DNA repair machinery (microsatellite instability) and the other due to incorrect chromosomal segregation during the cell cycle (chromosomal instability). Therefore, if we developed a drug targetting the mutated gene product in MIN, it would be very useful for these patients but ineffective in CIN patients. By screening for the gene we are able to apply the correct medical treatment.

2. Genetic analysis can be used to identify inherited genetic disorders and hence treat the patient earlier than at the presentation of first symptoms.

3. Every person has a unique genetic profile which may say things about their potential to develop certain conditions (for example schizophrenia, cancer, Huntingtons). On an individual level, the knowledge that you are predisposed to a condition (such as Huntingtons, which currently has no cure) may be hard to cope with. If an employer or insurance company were to get hold of a genetic profile, they would have the potential to make a decision based on your long term predisposition to given conditions, instead of basing decisions on your actual medical profile. There has to be, and I believe there is, a high level of regulation with regards to any genetic tests which are performed.

Maybe. But the knowledge is also being used to create viruses that target specific genetic make-ups.

Research the beginnings of IBM and Planned Parenthood