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I would like to talk about non-invasive prenatal diagnosis.
Prenatal diagnosis is now an established part of modern obstetric care.
However, conventional methods for
definitive prenatal diagnosis are invasive and constitute a finite risk to the fetus.
For this reason, over the last 40 years
many scientists around the world have been
researching the use of non-invasive prenatal diagnosis.
Today, I'd like to review with you one possible approach that is
based on the use of cell-free nucleic acids which are present in the plasma.
The discovery of circulating nucleic acids can be
traced back to a couple of French scientists in 1947,
who used a chemical method to demonstrate the presence
of nucleic acids in the plasma of healthy and sick individuals.
This work was remarkable, because this was done even before
the seminal work by Watson and Crick, who
demonstrated the double helix structure of DNA in 1953.
In a way we can imagine that the French scientists were
very much ahead of their time, because you can imagine that in the 40s
if you had told people that there were nucleic acids circulating in the plasma,
people would most likely ignore you.
Indeed, this is what happened.
The work of Mandel and Metais was forgotten for more than the next ten years
until the 1960s,
when people used immunoassays to demonstrate the presence of
large quantities of DNA in the serum of people with systemic lupus.
In the 70s scientists showed that in patients with cancers
there is always a high concentration of DNA in the serum,
but the origin of this DNA remained unknown until 1989, when Maurice Stroun from Switzerland proposed that
maybe some of these DNA molecules were released by the cancer cells.
Definitive proof had to wait until '94, when scientists used
PCR-based methods to show that tumor-derived
oncogene mutations could be detected in the plasma and serum.