In this paper, I will first describe the biology of genetic testing, and then discuss the pros and cons of predictive genetic testing. Before we start discussing how genetic tests are developed, let us discuss how genes can trigger disease. A sound body requires the action of many proteins working together. For a protein to function properly, an intact gene must encode for that specific protein. A mutation describes a gene which has been changed.
Mutations are beneficial if the fitness of an individual is enhanced.
Harmful mutations can either slightly alter a protein, where the protein may still minimally function, or they may totally disable a protein. Since we have determined how genes can trigger harmful effects in the body, we can now examine how scientists look for specific genes that cause diseases. Scientists, looking for a diseased gene, study DNA samples in individuals where the disease has been present in the family for many generations. They look for specific genetic markers, which are DNA segments that are identified in individuals with the disease, and not identified in healthy individuals. Scientists then narrow down the area of DNA by mapping a gene.