Rare Disorders Uncovered Through Complete Sequencing Of The Human DNA

Conceptual image of a cell karyotype exhibiting trisomy, three copies of one chromosome / Darryl Leja for NHGRI

According to a study by researchers at the National Institutes of Health and other institutions, extending noninvasive prenatal screening to all 24 human chromosomes can detect genetic disorders that may explain miscarriage and abnormalities during pregnancy. Because of the way data have been analysed, typical genomic tests performed during pregnancy have targeted extra copies of chromosomes 21, 18 and 13, but rarely evaluated all 24 chromosomes.

Extending [..] analysis to all chromosomes allowed [..] to identify risk for serious complications and potentially reduce false-positive results for Down syndrome and other genetic conditions.

The investigators analyzed DNA sequence data from nearly 90,000 samples of maternal plasma, the liquid portion of blood after all cells have been removed. Of these samples, 72,972 came from a U.S. cohort and 16,885 came from an Australian cohort. For each, researchers calculated a normalized chromosome denominator quality (NCDQ), which measures the likelihood that a sample has the standard two copies of each chromosome. Those with an NCDQ of 50 or below were flagged for further evaluation.


[..] found that pregnancies at greatest risk of serious complications were those with very high levels of abnormal cells in the placenta. [..] Results suggest that patients be given the option of receiving test results from all 24 chromosomes.

News Refrence Front Line Genomics

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