Medical Breakthrough for Down’s Syndrome Testing
Thanks to two new genetic tests, a drop of mother’s blood could soon be all it takes to say if an unborn baby has Down’s syndrome.
A child with Down’s syndrome inherits an extra copy of chromosome 21 from their mother or father. Now two teams of researchers have devised a simple blood test which they claim will detect this extra copy by simply analyzing fetal genetic material shed into a mom’s blood.
According to lead researcher Dennis Lo of the Chinese University in Hong Kong, this would reduce and even eliminate the need for invasive tests that can cause miscarriage. “This problem really appears to be solvable.”
In fact, Lo’s method is now being commercialised by Sequenom of San Diego in California.
The approach focuses on a stretch of chromosome 21 that is only expressed in foetuses. Sequenom detects this RNA and determines which parent it comes from by identifying the differences between individuals in single letter variations –single nucleotide polymorphisms, the New Scientist reported.
If the amount of chromosome 21 from each parent is about the same, the foetus is healthy, but if one is about double the other, the foetus probably has Down’s, according to the researchers.
In another research, Stephen Quake and colleagues at Stanford University in California have developed a Down’s test that doesn’t depend on single nucleotide polymorphisms (SNPs).
The team uses “shotgun sequencing” to sequence short DNA fragments in the mother’s blood. Subsequently, they map each fragment to specific chromosomes and calculate proportion from chromosome 21.
In their study, they analysed blood samples from 18 pregnant women, half of which had foetuses with Down’s. They found that these mothers had 11 per cent more chromosome — 21 fragments in their blood than the mum’s with healthy foetuses.
The findings have been published in the ‘Proceedings of the National Academy of Sciences’ journal.