Wednesday, September 10, 2008

Genetic testing

Genetic testing involves the direct examination of the DNA molecule itself. A scientist scans a patient’s DNA sample for mutated sequences.

There are two major types of gene tests. In the first type, a researcher may design short pieces of DNA (“probes”) whose sequences are complementary to the mutated sequences. These probes will seek their complement among the base pairs of an individual’s genome. If the mutated sequence is present in the patient’s genome, the probe will bind to it and flag the mutation. In the second type, a researcher may conduct the gene test by comparing the sequence of DNA bases in a patient’s gene to disease in healthy individuals or their progeny.
Genetic testing is now used for:

* Determining sex
* Carrier screening, or the identification of unaffected individuals who carry one copy of a gene for a disease that requires two copies for the disease to manifest
* Prenatal diagnostic screening
* Newborn screening
* Presymptomatic testing for predicting adult-onset disorders
* Presymptomatic testing for estimating the risk of developing adult-onset cancers
* Confirmational diagnosis of symptomatic individuals
* Forensic/identity testing

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