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I have a question I could not get an understandable reply from Google and I am no expert in the matter, so my plead to you is if you could give me practical and relatively easy to follow advice.

With the view of the breakthroughs in DNA research and all the anticipated applications to medicine in the near-future, I am willing to build a storage of the DNAs in my family (eg 20-30 people, some at a very old age). The use may not be for cloning :) but rather, for eg to map and trace specific hereditary genes when such services become more available to the wide public; and thus, probably help with a personalized medicine for someone, or find genome problems, and probably be able to 'turn them off' at some point.

Is there a way I can extract cells (ie from inside the cheek, or hairs), and store them for a few decades while preserving the DNA (eg put them in a freezer at -18C or in some solution)? I have only common knowledge in this area so apologies if the examples are silly, but I assume you can understand my point.

I would be grateful if you provide practical instructions as: "you buy 500ml of the chemical xx"; or "mix 150ml of xx and 200ml of zz", so me and anyone who finds the idea appealing, can follow. Ps-the lower the costs of the procedures, the better (I found some personal "dna vaults" costing several '000$).

Thank you for your consideration!

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If you have access to a laboratory (or at the very least a centrifuge and pipettes) and some laboratory experience you can extract the DNA from the cells which would be much easier to store. There are a number of commercial DNA extraction kits available that are easy to find on google and order online. I don't want to promote any particular brand but I've mostly used DNEasy made by Qiagen (really just because that's what I'm used to). All the step-by-step instructions are in the kit and all the reagents are also in the kit with the exception of 100% ethanol which should be easy to obtain.

If you have significant molecular biology experience and access to a full lab with a fumehood and appropriate safety installations you can try a manual extraction using trizol or phenol-chloroform. This would be slightly cheaper however given the toxicity of these agents I wouldn't recommend this for you. It really doesn't sound like you have these resources available to you.

Once you have the DNA extracted you can dilute it in Tris-EDTA or the elution buffer that comes in the kit. You can store extracted DNA in a regular fridge (4C) for several years. If you're looking to store for decades you may want to rent space in a -80C freezer but this would be more expensive. A fridge may be just right to suit your needs. You should be careful that this fridge has a backup power supply.

I should be clear that although extracting DNA is the easiest way to do this for somebody with experience, you should not try if you don't know what you're doing. Some of these reagents are dangerous and you are likely to ruin the samples you've taken from your family members and end up with no DNA at all. Good luck!

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So cryopreservation would be the long-term mode of storage, and you'd do something like store your sample in a cryonic freezer supplied w/ liquid nitrogen at -196C. Cellgro provides some recommendations for cryopreservation here. Keep in mind, cryonic freezers are typically pricey, but broady, the idea is you need to keep your cells at the right temperature, in the right media. The source I gave you provides suggestions for media, DMSO as a cryoprotectant, and a protein source to protect the cells during the process. Also, keep in mind there are recovery issues with cryopreservation. There's some data to suggest reactive oxygen species, and apoptosis mechanisms damage/fragment the DNA in cells that have undergone that sort of freezing(1, 2, 3). These articles mainly refer to sperm storage.

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  • $\begingroup$ I don't think OP is asking about storing live cells, but rather DNA. You certainly don't need liquid nitrogen for that, once you've purified it. $\endgroup$ – MattDMo Apr 12 '15 at 0:01
  • $\begingroup$ Thank you for the idea, surely it is an option one can choose. I assume the costs would be for a space in such a freezer, shippings and to hire some pro. to do the procedures you bookmarked. As MattDMo added, cryopreservation seems to be a way used mostly to preserve cells alive (we did that with our child's embryo-cord, as many parents do). I have a feeling there are even some simpler ways to preserve ONLY dna which can be analyzed after a while; I think of biologists being able to evaluate dna extracted from the remains of species long been extinct, or early humans. $\endgroup$ – krous Apr 19 '15 at 11:43
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You could store DNA diluted in water at -20C for a very long time. The only problem with at home storage would be the type of freezer most households have. These come standard with defrosting feature, which thaws up the freezer to remove the ice accumulation... This would affect the stability of the DNA at long term scale. Having a styrofoam box to protect the samples could however dampen the elevation of temperature around your DNA.

As for the DIY extraction, most extraction methods use either chloroform or chaotropic salts... those are very toxic and dangerous. A "dirty" extraction would be the best approach. You would still need a centrifuge, NaOH, EDTA, and Tris Base for a very simple approach (1). The referenced protocol is prescribed for rodent tissue, but could be applied to small skin snips or buccal frottis (not that I recommend ripping skin from your relatives...).

For the various reagents, Sigma-Aldrich sells pure chemicals, but I have no idea if particulars can buy on their website.

(1) http://jaxmice.jax.org/support/genotyping/dna-isolation-protocols.html

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Basically agree with the other answers, but a bit of clarification. The bottom line here is that DNA is actually a really stable molecule - after all, it's evolved to be! So assuming your principal goal is 'keep enough DNA that you can read genomes and/or epigenomes'*, the main requirements for storage are low and steady temperatures. For instance ancient DNA studies regularly collect partial DNA, and even whole genomes, from organisms including humans that are thousands of years old. The key here is temperature stability.

So with that in mind:

1) I'd keep two samples, a DNA extraction** and some whole tissue. This might mean cheek swab, some blood, something like that. There's lots of material out there. Teeth are pretty good, if any of those come your way!

2) 'Cryo' stuff (at least in the UK) would be taken to mean 'very cold, something to do with cryonics, and generally aimed at preserving whole life etc'. This is way out of scope for the OP even if you agree the (contentious) claims those practitioners make.

3) Can't emphasise enough that domestic freezers won't cut it. In general you can DIYbio / hack lots of lab kit that's overpriced (water baths, gels, even PCR machines can be bodged to a degree) but as mentioned above, domestic kit will defrost periodically (even assuming you have a UPS to guard against power outages) and those temperature fluctuations will shred your DNA.

4) One final thought, bearing in mind 100yr-old DNA at -4 is probably going to be in better shape than 20yr-old DNA at -80 with periodic warming: You don't, by any chance, happen to live near any glaciers, do you? Because if so you might as well make a bio-time capsule: the ultimate backup! ;)

Either way - good luck.


*Mind you, the simplest thing to do is sequence your relatives' genomes now? Or are you waiting for costs to fall?

**The reason to keep a whole tissue sample as well as extracted DNA is this: While extracted DNA is likely to be more stable over very long periods of time, current DNA extractions have been optimised to work well with current DNA sequencing techniques but may inhibit future ones. For example, some of the well-established Tris-EDTA step https://biology.stackexchange.com/users/15594/jack mentions are contraindicated for Oxford Nanopore (MinION/PromethION) sequencing preps IIRC.

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At page 12 of this pdf there is an easy protocol for DNA extraction from saliva. You just need soap and salt to do it (it works even without Chelex, but you get better DNA quality if you use it). A microcentrifuge is requested for this protocol, you can find them on eBay for less than 100 dollars. If the max speed is not high enough you can always spin for a longer time at lower speed. I tried it and it works.

Once you have the DNA, you can store it in a normal freezer (-20) for decades, just avoid to defrost it a refreeze it multiple time or it will deteriorate.

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