The potential for understanding human genetics increased greatly when the Human Genome Project successfully identified and mapped all the genes on human chromosomes in 2003. Genetic techniques can be used to study individual genes to learn more about specific disorders. For example, some kinds of disorders that have been classified based on what symptoms they caused have been reclassified based on what the genetic abnormality is.
Genetic tests are used to diagnose certain disorders (for example, hemochromatosis and chromosomal disorders such as Down syndrome and Turner's syndrome). Genetics is also increasing the ability to predict what disorders a person is likely to develop. For example, women with certain abnormalities in the BRCA genes are prone to develop breast and ovarian cancers. These predictions may allow disease prevention and screening to be tailored much more to each person. Advances in techniques that assess people's genetic characteristics and increased understanding of human genetics have improved diagnosis of genetic disorders before birth. Genetic screening can be used to counsel parents about the risks of passing on a genetic disorder to their offspring (see Genetic Disorders Detection: Genetic Screening). Screening can also be used to detect fetal abnormalities (see Genetic Disorders Detection: Prenatal Diagnostic Testing).
Increased understanding of human genetics has the potential to predict how people, depending on their precise genetic makeup, will respond to certain treatments. For example, specific genes can predict how much warfarin, a blood thinner, a person is likely to require. This prediction is important because taking too much warfarin can cause serious bleeding and taking too little makes the drug ineffective, which is also risky. Gene analysis can also predict whether a person will have intolerable or only minor side effects when taking irinotecan, an anticancer drug. People likely to have intolerable side effects can be treated with a different drug.
Last full review/revision August 2007 by Judith G. Hall, MD