For example, before geneticists cloned the DMD gene, the confirmation of a diagnosis required expensive and uncomfortable tests, and the tests were inadequate to detect carriers. Now, with only a blood sample, geneticists can detect most mutations associated with DMD very rapidly. DNA-based tests clarify the diagnosis quickly and enable geneticists to detect carriers within the same family. In addition, some tests such as that for cystic fibrosis cannot detect all of the mutations associated with the disorder. The use of genetic tests to detect carriers, for prenatal diagnosis and for presymptomatic diagnosis, has created ethical and public policy issues.
Genome information can indicate the future likelihood of some diseases.
For example, if the gene responsible for Huntington's disease is present, it is a near certainty that symptoms eventually will occur, although geneticists cannot accurately predict the time of onset. Genome information also helps geneticists predict which individuals have an increased susceptibility to disorders such as heart disease, cancer, or diabetes, which result from complex interactions between genes and the environment. There is no guarantee that symptoms will occur, but the risk is greater for individuals with specific genotypes than for the general population. Insight into Basic Biology Information generated by the HGP may shed light on several interesting biological questions. The discovery of new genes is an obvious benefit, as is the determination of their functions.