Copy number variations (CNVs), which are deletions or duplications of large chunks of the genome, are a major cause of birth defects, intellectual disability, autism spectrum disorder, and other developmental disorders. Still, geneticists can definitively say how a CNV, once discovered in someone's DNA, leads to one of these conditions in only a very small fraction of cases. To aid in the interpretation of CNVs, researchers at Emory University School of Medicine have completed detailed maps of 184 DNA duplications found in the genomes of individuals referred for genetic testing. The findings have published online in the American Journal of Human Genetics (AJHG) and are currently available (see link below). "Ours is the first study to investigate a large cohort of clinically relevant duplications throughout the genome," says senior author Katie Rudd, Ph.D., Assistant Professor of Human Genetics at Emory University School of Medicine. "These new data could help geneticists explain CNV test results to referring doctors and parents, and also reveal mechanisms of how duplications form in the first place." Despite advances in "next-generation" DNA sequencing, the first step for patients who are referred to a clinical geneticist is currently microarray analysis. This is a scan using many probes across the genome, testing if someone's DNA has one, two, three, or more copies of the DNA corresponding to the probe (two is the baseline). From this scan, geneticists will have a ballpark estimate of where a deletion or duplication starts and ends, but won't know where the breakpoints are exactly. "In a few years, advances in sequencing will make it possible to routinely capture data on copy number variation and breakpoints at the same time," Dr. Rudd says. "But for now, we have to do this extra step."
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