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I was wondering, when is it possible to extract cells (humans or mice) in order to sequence them and detect diseases. Extra: Urine of the embryo in humans is excreted in the 16th week, so I guess that then it's possible to extract some embryo cells.

EDIT In other words, when is it possible to grab enough DNA to know the full genome of the embryo without damaging it? In order to sequence it and avoid most genetic diseases and regulate the weekly abortion limits.

Thanks

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  • $\begingroup$ In vivo or in vitro? $\endgroup$ – swbarnes2 Oct 25 at 20:47
  • $\begingroup$ Sorry, in vivo, now I'll edit. $\endgroup$ – Héctor Oct 25 at 20:48
  • $\begingroup$ So you are discounting human non-invasive pre-natal testing, on the grounds that it uses cell-free DNA? $\endgroup$ – swbarnes2 Oct 25 at 20:50
  • $\begingroup$ @swbarnes2 it depends, I am especially thinking in the abortions and genetic diseases. $\endgroup$ – Héctor Oct 25 at 20:54
  • $\begingroup$ So, when are there enough cells to grab enough DNA and fully genotype the embryo?, Then you could know most genetic diseases. My question would be answered. $\endgroup$ – Héctor Oct 25 at 20:56
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As usual, the answer is "it depends what you mean". There is a large existing field (prenatal genetic diagnostic testing) which trying to diagnose genetic diseases in fetuses using different technologies. These technologies are described more in points 2 and 3 below, whereas point 1 is a somewhat academic statement about the technical capabilities of genomic technology in pure research settings which are currently not really relevant for medical applications.

I can think of 3 different answers to the question as originally posed:

  1. With currently available sequencing technology you can never know the full genome sequence of a human well enough to see all the potentially damaging variants. The "finished" human reference genome in fact has gaps and errors that are constantly being corrected. For more information about what "finished" means, see here. Only one assembly of a telomere-to-telomere human chromosome exists as far as I know, and that's only the X chromosome. Even accepting that this best available technology is good enough, it also relies on things like the ability to isolate lots of high-molecular-weight DNA, which makes it very tough to do on the amount of cells you could get from a newborn without highly invasive procedures such as e.g. sampling fetal tissue in vivo. My guess is that even amniocentesis would be very hard to get good HMW DNA from.

  2. With currently available sequencing technology you can however test very early provided you used IVF, at least as early as the 100-cell stage (probably earlier). This is a chancier method that will miss a lot of information but gives you good enough info to diagnose aneuploidies or other very obvious variants.

  3. Alternately, you can screen cell-free fetal DNA as early as 7 weeks (or possibly earlier). However this does not involve isolating cells so it is potentially not what you are thinking about. It is somewhat better information than preimplantation screening, but rather worse information than you can get from whole cells.

Likely none of those are exactly the answer you want, but it's also a less simple question than it appears at first: a) getting cells is hard and probably not necessary for the current tech, and b) the tech isn't actually as good as generally advertised.

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  • $\begingroup$ Thanks!, It is a good and really complete answer. Hopefully in the future we will be able of doing a more complete sequence of the embryos or fetus and avoid those diseases developed during the development. Do you know any source (blog, researcher wordpress...) that talk about this area? Or the scientific name of this field? Thanks!! Héctor $\endgroup$ – Héctor Oct 28 at 19:10
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    $\begingroup$ @Héctor - see edit. I think you are interested in prenatal genetic diagnostics. I have added a link to the answer, which you can also see here: acog.org/Patients/FAQs/… $\endgroup$ – Maximilian Press Oct 29 at 4:11
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    $\begingroup$ Oops, meant to also link to this article: obgyn.onlinelibrary.wiley.com/doi/full/10.1002/pd.5520 and there is a journal "Prenatal Diagnostics" that you may find useful: obgyn.onlinelibrary.wiley.com/journal/10970223 $\endgroup$ – Maximilian Press Oct 29 at 4:11

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