DNA Based Diagnosis of Genetic Diseases
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Current medical advances make it possible to use DNA to diagnose genetic diseases of various kinds. Genetic disorders are variations in genetic material that cause an abnormality. Diseases such as Down syndrome, cystic fibrosis and sickle cell anemia can be diagnosed before a child is born, improving chances of treatment. Adults who have family history of breast cancer or Alzheimer's disease are also able to check their probability of having these disorders later in life.
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Tests for genetic disease are conducted by using DNA samples extracted from blood or other tissue samples if necessary. Some DNA mutations can be seen under a microscope, such as a deleted or added chromosome. A missing or extra part on a chromosome would also be visible with a microscope. Smaller alterations to the chemical make up of the gene results in missing or inactive genes, as well as too many occurrences of the same gene.
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Chromosomes can end up placed in the wrong order or turned around in a different direction, causing the gene to not function at all. Examples of these mutations include the three copies of chromosome number 21, which produces Down syndrome, and the mutation on chromosome 7's long arm, which results in cystic fibrosis.
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In order to find defects in chromosomes, it is necessary to use more extensive genetic testing to examine a molecule of DNA. One type of genetic testing involves the creation of small pieces of DNA that mimic mutated DNA in a person. These pieces, called probes, will search the genome of a person to attempt to find a sequence similar to itself. If found, the probe will attach to the mutated gene, showing the presence of that gene in the patient. An alternate DNA test used compares a part of the tested gene with the sequence in a normal gene.
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