Basics
Genetic testing uses a sample of DNA-containing material like blood, saliva and amniotic fluid to search for variations in chromosomes (where genes are stored), genes and proteins (which control genetic action). There are many different procedures used in genetic testing and many different reasons for their use.
DNA Amplification
Genetic testing can be done on very small samples. However, when more DNA is required for testing than is available, it can be amplified (copied over and over) through processes like polymerase chain reaction, which copies a DNA molecule by stimulating the DNA-reproduction process.
Karyotyping
Conditions such as Down's (trisomy) and Turner's (monosomy) syndromes, which are caused by the inheritance of an extra (Down's) or one too few (Turner's) chromosomes can be revealed through karyotyping, which creates an image of the chromosomes found in an individual's somatic (non-gonadal) cells. This is one of the simplest forms of genetic testing as no molecular study is necessary.
Molecular Study
Genetically linked conditions have a standard form for healthy, sick or at-risk individuals. Genetic testing can isolate things like deletion or mutation of a gene or protein and either confirm a diagnosis or alert one to the risk of developing a condition. For instance, a genetic screening test can alert an at-risk individual whether he will develop Huntington's chorea years or even decades before symptoms develop.
Why Genetic Testing is Done
Genetic testing can be done to determine the health of a fetus or newborn, the presence or risk of a genetically linked condition, whether an individual is a carrier for a condition and lineage as well as for crime-scene investigation.
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