This means that their emergence and strength does not depend on the status of a single gene but on anything between two and twenty genes or more. This makes genetic analysis by conventional means almost impossible and also represents a very arduous challenge for molecular genetics. In medicine a diagnosis is the identification of a disorder on the basis of symptoms or of any correlation such as environmental pre-requisites. A precise diagnosis is fundamental to effective medical practice. These deductions can become under some circumstances predictive.
Predictive diagnosis can prevent the emergence of problems.
Unfortunately there are relatively few examples that allow predictive diagnosis based on the physical properties of an individual. Due to this lack of predictability, we are exposed to a large number of risks without having the faintest idea. But since many of those pre-dispositions are encoded in our genetic layout modern medical genetics offers a new possibility in this respect. Recent studies have established that between one quarter and one third of the eight percent of women that develop breast cancer are genetically predisposed to a higher risk of this disorder. Similarly, there are genetic pre-dispositions to a higher risk of prostate cancer and colon cancer.