(See also Genes and Chromosomes Genes and Chromosomes Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body or the code for functional ribonucleic... read more .)
The potential for understanding human genetics increased greatly when the scientists behind 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 routinely used to diagnose certain disorders (for example, hemochromatosis Hemochromatosis Hemochromatosis is a hereditary disorder that causes the body to absorb too much iron, causing iron to build up in the body and damage organs. In the United States, over 1 million people have... read more and chromosome disorders such as Down syndrome Down Syndrome (Trisomy 21) Down syndrome is a chromosome disorder caused by an extra chromosome 21 that results in intellectual disability and physical abnormalities. Down syndrome is caused by an extra chromosome 21... read more and Turner syndrome Turner Syndrome Turner syndrome is a sex chromosome abnormality in which girls are born with one of their two X chromosomes partially or completely missing. Turner syndrome is caused by the deletion of part... read more ).
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 breast cancer Breast Cancer Breast cancer occurs when cells in the breast become abnormal and divide into more cells uncontrollably. Breast cancer usually starts in the glands that produce milk (lobules) or the tubes ... read more and ovarian cancer Ovarian Cancer, Fallopian Tube Cancer, and Peritoneal Cancer Ovarian cancer is cancer of the ovaries. It is related to fallopian tube cancer, which develops in the tubes that lead from the ovaries to the uterus, and peritoneal cancer, which is cancer... read more . These predictions may allow disease prevention and screening to be tailored much more to each person.
Diagnosing genetic disorders before birth
Advances in techniques that assess people’s genetic characteristics and increased understanding of human genetics have improved diagnosis of genetic disorders before birth. In some cases, genetic disorders that are diagnosed before birth can be treated after birth or sometimes before, which prevents future complications. For example, corticosteroids given to the mother before birth may decrease the severity of a type of genetic hormone deficiency in the offspring.
Genetic screening Genetic Counseling and Genetic Testing Before Pregnancy Genetic disorders are caused by abnormalities in one or more genes or chromosomes. Some genetic disorders are hereditary and others are spontaneous. Hereditary genetic disorders are passed down... read more can be used to counsel parents about the risks of passing on a genetic disorder to their offspring. Screening can also be used to detect abnormalities in a fetus (Prenatal Diagnostic Testing Prenatal Testing for Genetic Disorders and Birth Defects Prenatal testing for genetic disorders and birth defects involves testing a pregnant woman or fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including... read more ).
Did You Know...
Responding to drugs
Increased understanding of human genetics has the potential to predict how people, depending on their precise genetic makeup, will respond to certain drugs (Genetic Makeup and Response to Drugs Genetic Makeup and Response to Drugs Differences in genetic (inherited) makeup among individuals affect what the body does to a drug and what the drug does to the body. The study of genetic differences in the response to drugs... read more ). For example, specific genes can predict how much warfarin, an anticoagulant ("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.
Gene analysis can also determine how quickly people metabolize and thus respond to codeine, an analgesic. People who metabolize codeine rapidly can accumulate high levels of a metabolic byproduct of codeine that impairs their unconscious drive to breathe. This effect of rapid metabolization resulted in the death of some children who were given codeine after tonsillectomy and adenoidectomy were done to treat obstructive sleep apnea.
The genetics of diseased tissue (such as cancers) can help drug manufacturers identify more precise treatment targets when developing drugs (such as anticancer drugs). For example, the anticancer drug trastuzumab can target specific cancer cells in breast cancers that involve the breast cancer gene HER2/neu.
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Human Genome Project: Information about the international, collaborative research program mapping and understanding all of the genes of human beings, known as the human "genome"