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I learned that a rare and unique giant Chinese Paddlefish recently became extinct. I'm wondering if samples of DNA were collected by scientists to allow reviving of the specie in the future.

My quick Google check only revealed one paper that studied DNA of the fish 15 years ago - so there is a possibility that some DNA information exist out there. But is it enough to restore the species?

I'm interested in learning about any organisations or projects that would systematically collect genetic material of all endangered species. Is there a way to ask them about this specific fish?

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Informally speaking, there is no real/good way to bring back extinct species. Especially sexually reproducing species; you'd need to revive a male and a female at the very least, and these are markedly different genomes due to unique sex chromosomes.

Some 'bad ways' exist though; in principle, if you found a perfectly preserved nucleus (the organelle that holds genomic DNA of most eukaryotes), it may be possible to insert this nucleus into a sibling or sister species (e.g. wooly mammoth nuclei into denucleated elephant zygotes). This would be the cloning approach. However, you then run into practical issues. You have to guarantee that this embryo will implant itself, which itself is not always the case. The nucleus and chromosomes must also be intact enough (which may not be the case after storing them, e.g. in ice, which may require thawing which often damages cellular structures) to create a rather healthy, fertile organism that will breed at a sufficient rate to restore a stable population. These and many more complications will reduce your chance of rescuing an extinct species to near-zero. Even then, one could argue that it is an incomplete de-extinction because you've only substituted the genomic DNA, and not other parts of the genome (e.g. chloroplast or mitochondrial genomes) which are part-and-parcel of the genetic signature that makes a species a species.

Alternatively, you can create hybrids where fragments of DNA from extinct species are brought into the genomes of similar existing species, by molecular methods such as recombination using CRISPR/Cas9. Here though you are only creating hybrids, not reviving extinct lineages. The extent to which you could do this is also limited and you would have to increasingly troubleshoot why a hybridization didn't work the more host genome you replaced with the extinct species' genome. Transgenesis using individual genes (say, transfering an enzyme into a new organism) is quite plug-and-play, but replacing entire chromosomes would be near impossible to pull off, not least because you would have little insight into why things aren't working - only that they aren't.

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