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Andrey Machikhin

U.S. researchers say they can accurately determine the genome – or genetic blueprint – of a fetus by an alyzing DNA samples from both parents.Their work could pave the way to prenatal screening tests that reduce the need for invasive procedures such as amniocentesis and chorionic villus sampling. (In these procedures, a needle or catheter is inserted into the womb to obtain fetal DNA.)

It has long been known that about 10 per cent of the free-floating DNA in the mother's bloodstream comes from the fetus. The remaining 90 per cent, of course, is from mom.

In theory, that means researchers have relatively easy access to fetal genetic material that can be scrutinized for signs of inherited diseases. But the problem is that the free-floating bits of fetal DNA do not provide a complete picture. They are just fragments. What's more, there is no obvious way to distinguish between the fetus's DNA and mom's DNA.

So researchers at the University of Washington in Seattle set out to reconstruct the complete fetal genome by comparing the DNA fragments to the genomes of the mother and father.

They used a combination of advanced gene sequencing and statistical modelling to determine what parts of the baby's genetic material had been inherited from the mother and what had come from the father.

They also looked for evidence of new mutations that may have that occurred during egg or sperm formation.

"We attempted and mostly succeeded in reconstructing the whole genome sequence of a fetus," said Jay Shendure, the senior author of the study published in the journal Science Translational Medicine.

The process still needs some refinement. But Dr. Shendure thinks this approach can potentially predict if a child has acquired genetic variants linked to a wide range of disorders such as cystic fibrosis, Huntington's disease and sickle-cell anemia.