The majority of genetic diagnostic testing is done with sequencing, which identifies each base, or "letter)' in a string of DNA. Sequencing can be used to identify all of the roughly three billion base pairs in a human genome, but most clinical testing is limited to sequencing single genes, which can reveal the presence of a mutation that could result in a disease or other disorder. In research, scientists use newer techniques that can scan millions of strands of DNA in parallel-a faster, cheaper process that providesrnvast amounts of genetic data. But these advanced sequencing tests have yet to be approved or optimized for the practice of medicine.
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