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By "types," I mean several different species of animals. If, post extraction, the pure, isolated DNA of several different animals were mixed together and run through DNA analysis, I know the results would be inconclusive, but would there be any usable information returned at all? Would any species be individually identifiable?

The scenario is hypothetical and for a TTRPG plot; the players procured samples of a substance that they don't yet know are isolated DNA polymers (think the "extracting strawberry DNA" science experiment for children) from several different species of animals and a couple of humans, which was mixed together post-extraction. They'd like to have the DNA samples analyzed. Handwaving turnaround time (I know this process would realistically take weeks to months at the bare minimum, but if crime procedurals can deus-ex analysis results in 48 hours, so can my players), what would that analysis turn up?

Would they be able to parse specific species, or the ratio of one species to another (ie the sample only containing one or two dogs, but many, many small birds and squirrels)? They almost certainly wouldn't be able to turn up any kind of identifiable information on the human DNA, even with an uncontaminated reference sample, right?

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    $\begingroup$ I'd push back on your turnaround time in the real world; depending on the technique, the motivation of the people involved, and access to equipment/reagents, this could be accomplished in a couple hours (PCR assays) to a couple days (DNA sequencing+analysis). $\endgroup$
    – Maximilian Press
    May 31, 2022 at 17:44
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    $\begingroup$ In your TTRPG you can kind of do whatever you want, but I guess I'd keep in mind that there isn't a "ANALYZE DNA" button you push on some biology machine in the real world; what you output very much depends on what you go about trying to accomplish. $\endgroup$
    – Bryan Krause ♦
    May 31, 2022 at 18:37

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You may be interested in commercially available meat testing kits - DNA kits have been widely used to detect what certain food products are actually (or are actually not) made of. Some kits are designed to identify the presence/absence of a dozen or more animal species, which can be reliably detected at proportions even less than 1% of the total sample. There have been some high-profile cases of meats labelled beef or pork actually turning out to be horse, for example, which was revealed by DNA testing. It is quite routine to be able to identify what species of animal are present in a mixed DNA sample, and to estimate their contribution to the mix.

At a practical level, this gets more difficult the more species you have in the mix, the less you know about what's in the mix, and as the concentration of any contributor decreases. But in principal, if the DNA is there, it can be sequenced and identified bioinformatically. It would be feasible to isolate human DNA from a mix of many animals, although you'd have a harder time with highly conserved genomic regions that are consistent across many species. But there are some regions of the genome that are uniquely human, which could be used positively ID a particular human's DNA among a mix of different species.

Overall, you can in theory learn a lot from a mixed-DNA sample, including the species present, their relative contribution, and even tell apart individuals within a species and identify whether any of the DNA matches the reference of a particular individual.

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    $\begingroup$ Minor criticism: while I expect there to be readily google-able support for this answer, it's handy to have a specific trustworthy source linked in an answer. $\endgroup$
    – Maximilian Press
    May 31, 2022 at 17:41

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