What is Genetic Testing? How Does It Work?

Genetic testing (also called DNA-based tests), the latest and most sophisticated techniques used to detect genetic disorders, involve direct examination of the DNA molecule itself. Other genetic tests include biochemical tests for gene products as enzymes and other proteins and for microscopic examination of chromosomes colored or fluorescent.

Genetic testing (also called DNA-based tests), the latest and most sophisticated techniques used to detect genetic disorders, involve direct examination of the DNA molecule itself.  Other genetic tests include biochemical tests for gene products as enzymes and other proteins and for microscopic examination of chromosomes colored or fluorescent.  Genetic tests are used for various reasons, including:

Detection of carriers, which involves identifying unaffected individuals who carry one copy of a gene for a disease that requires two copies of the disease expressed

* Pre-implantation genetic diagnosis (see box, disease embryos Detection)

* Prenatal diagnostic tests

* Newborn screening

* The presymptomatic testing for predicting the occurrence of disorders in adulthood, such as Huntington’s disease

* Presymptomatic testing for estimating the risk of adult cancer develops Alzheimer’s disease

* Confirmation of the diagnosis of a symptomatic person

* Determination of Forensic Identification /

Human DNA Chart
Disease screening of embryos

Preimplantation genetic diagnosis (PGD) is a test that detects genetic defects of embryos used in IVF.  With PGD, DNA samples from embryos created in vitro by the combination of an egg from the mother and father semen is analyzed for genetic changes that may cause problems.  Fertility specialists can use the results of this analysis to select only mutation free embryos for implantation in the uterus of the mother.

Before PGD, couples at high risk of conceiving a child with a particular disorder would begin pregnancy and then undergo chorionic villus sampling in first trimester or amniocentesis in the second quarter to test the fetus for the presence of the disease.  If the fetus tested positive for the disease, the couple faced the dilemma of whether to terminate the pregnancy.  With PGD, couples are more likely to have healthy babies, although the CIO has been practiced for many years, offers only a few centers in the world that procedure.

In genetic tests, scientists scan a patient sample for DNA sequences mutated.  A DNA sample can be obtained from all tissues, including blood.  For some types of genetic tests, according to researchers design of small pieces of DNA probes, which sequences are complementary to the mutated sequences.  These probes are looking for their complement among the three billion base pairs of the genome of an individual.  If the sequence of the mutation is present in the genome of the patient, the probe bind to it and flag the mutation.  Another type of DNA testing involves comparing the sequence of DNA bases in the gene of a patient with a normal version of the gene.  Test costs can vary from hundreds to thousands of dollars, depending on the size of genes and the number of mutations tested.
What are some pros and cons of genetic testing?

Genetic testing has already much better life.  Some tests are used to clarify the diagnosis and direct a physician to appropriate treatment, while others allow families to avoid having children with devastating diseases or identify people at high risk for preventable diseases.  dynamic monitoring and removal of colon cancer who inherit a gene for familial adenomatous polyposis, for example, has saved many lives.  On the horizon are genetic tests that provide physicians a simple test to diagnose a common disease of iron storage, turning a usually fatal condition to be treated.

commercialized genetic tests for diseases in adulthood, Alzheimer’s disease and some cancers are the subject of much debate about genetic testing.  These tests are aimed at health (presymptomatic) people who are identified as high risk because of strong family history of medical illness.  The tests provide only a probability of developing the disease.  One of the most serious limitations of these sensitivity tests is the difficulty in interpreting a positive result because some people carry a mutation associated with the disease never develop the disease.  Scientists believe that these mutations can act in concert with other mutations or environmental factors to cause disease.

One limitation of all medical examinations, the possibility of laboratory error.  These may be due to a misidentification of the sample, contamination by chemicals used for testing, or other factors.

Many in the medical community considers the uncertainty surrounding the interpretation of tests, the current lack of medical options available for these diseases, the potential of evidence “from the anxiety it causes, and the risk of social discrimination and stigmatization could outweigh the benefits of screening.

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