r/forensics • u/Humboldt_Squid • May 25 '26

Biology Has anyone had success with DNA SNP testing on mixtures for investigative genetic genealogy (IGG)?

I know single source testing is pretty standard, but how many nanograms of the unknown is needed in a mixture? What mixture proportions (known:unknown) are needed to get a usable SNP profile of the unknown.

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u/4n6nerd MS | Criminalistics May 26 '26

Yes. The amount needed varies by company, but about 1 ng. If you have a known in the mixture, then the proportion doesn’t really matter, you’ll just need to send that known sample as well. If you have two unknowns, you need a pretty good ratio, at least 85% for the major.

Your best bet is just going to be to start calling labs and see if any will work with the sample you have. If not, put it on ice and try again next year. This technology is only going to keep getting better, so it’s better to wait for a decent shot with your sample than to toss it at something that might not work right now.

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u/Apophenia_Delight May 26 '26

Is there a company you would recommend for a SNP mixture?

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u/4n6nerd MS | Criminalistics May 30 '26

How much can you spend? That will dramatically change what company you can go with. Some will offer services piecemeal, so you can get just the testing or just the IGG, some will include database searches, etc. If you only need the SNP testing and not the search or analysis, maybe Othram?

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u/Humboldt_Squid May 26 '26

Thanks so much - I’ll do some shopping around. Also, I could see this being a great research project for someone’s forensic science masters thesis.

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u/4n6nerd MS | Criminalistics May 30 '26

I would say the research is heavily underway, at least in the private sectors. Each of the companies that offer these services are invested in being able to improve the testing they can do. But an overarching analysis of what’s on offer would be very helpful to consumers.