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Genetics is defined as the science of genes, the variation of organisms, and heredity. In modern research, genetics provides essential techniques and tools in the investigation of a particular genes' function, such as analyzing genetic interactions. The clinical uses of genetics are expanding everyday, but regardless of technique or advancements they are used to make diagnoses, for genetic screening, to treat disease, in pharmacogenomics, and gene therapy.
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Genetic testing is very useful in diagnosing a variety of disorders, such as Klinefelter's syndrome, hemochromatosis, and Turner's syndrome. When a genetic disorder is diagnosed it often indicates that the affected person's relatives should also be tested to determine whether they are a carrier of the specific mutation or whether they have the genetic defect themselves.
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One of the most vital clinical uses of genetics is genetic screening. It is indicated for a variety of reasons, but it is most often used if a genetic disorder or mutation runs either in families or in populations. However, in order to justify screening an entire population the prevalence must be high enough because genetic screening is expensive. One goal of prenatal screening is to look for asymptomatic parental heterozygotes that carry a gene for a recessive disorder. For example, African Americans are screened for sickle cell anemia, Ashkenazi Jews are screened for Tay-Sachs disease, and many ethnic groups are screened for thalassemia. If the mate of a heterozygote is a heterozygote too, there is a risk that the couple will have an affected child. Prenatal diagnosis can be pursued if the risk is deemed high enough with methods, such as amniocentesis, umbilical cord blood sampling, fetal imaging, chorionic villus sampling, and maternal blood sampling. Certain genetic disorders that are diagnosed prenatally can be treated in order to prevent complications. For example, the effects of galactosemia, phenylketonuria, and hypothyroidism can be minimized or eliminated through replacement therapy or a special diet. The severity of the genetic disorder known as congenital virilizing adrenal hypoplasia may be decreased by giving corticosteroids to the mother before birth.
Those who have a family history of a disorder that is dominantly inherited and manifests later in life may consider screening so that they can decide whether to take the steps necessary to protect themselves against the disorder. Examples include BRCA1 or BRCA2 gene mutations that can increase the risk of several cancers, such as breast and ovarian cancer, and Huntington's disease.
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Therapy can sometimes be more informed and guided when the molecular and genetic basis of disorders is understood. For example, the compounds that are toxic to patients with genetic defects, such as homocystinuria and phenylketonuria, can most often be eliminated with dietary restriction. Other agents, such as vitamins, can reduce a compounds' toxic level by modifying the biochemical pathway. Therapy may also involve blocking an overactive pathway or replacing a deficient compound.
This is a type of treatment that studies how a person's genetic characteristics can affect how they respond to drugs. One element of pharmacogenomics is how pharmacokinetics are affected by genes. A person's genetic characteristics may help to predict how they will respond to treatment. For example, how a person metabolizes warfarin is partly determined by gene variants for the vitamin K epoxide reductase complex protein 1 and for the CYP2C9 enzyme. Genetic variations, such as in the production of UDP-glucoronosyltransferase 1A1, can help to predict whether irinotecan, an anticancer drug, will produce adverse side effects that are intolerable for the patient. Pharmacodynamics is another aspect of pharmacogenomics that studies how drugs will interact with cell receptors.
Gene therapy is a type of treatment that changes gene function. It is often described as inserting normal genes into the cells of a person who does not have normal genes due to a specific genetic disorder. There are several different methods used to do this, such as viral transfection, liposome insertion, antisense technology, and chemically modifying gene expression.
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Merck Manuals. (2007). Clinical Uses of Genetics. Retrieved on March 30, 2010 from Merck Manuals:http://www.merck.com/mmpe/sec22/ch327/ch327h.html
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