How would I store human DNA for decades, at room temperature, blood samples and not too invasive methods available. It needs to be 100% undamaged and usable for genome mapping.
I was rather thinking of a DIY method, not that I don't have paper I can drape in blood.I believe for military purposes (identification of bodies) they store blood poured on some kind of (blotting) paper and dried out. There is a printed sheet with form to fill and two empty circles where the blood is poured on to dry. No idea if it is kept at room temperature nor what kind of paper they use, but there is no doubt they have the technology and it is rather simple.
And here is an example of the method being employed in a practical setting:The reason for stability of DNA, RNA or protein could be attributed to the fact that the biological material binds to the matrix of the filter paper and the process of drying excludes water which is an important factor necessary for protease or nuclease to act. Binding of the biological material also binds several inhibitors which may interfere with various nucleic acid amplification methods.
Dried blood spots (DBS) on filter paper facilitate the collection, transport, and storage of blood samples for laboratory use. A rapid and simple DNA extraction procedure from DBS was developed and evaluated for the diagnosis of human immunodeficiency virus type 1 (HIV-1) infection in children by an in-house nested-PCR assay on three genome regions and by the Amplicor HIV-1 DNA prototype assay version 1.5 (Roche Molecular Systems).
They used PCR techniques to amplify the genetic material in the dried blood spot sample. In this case, they're testing for viral DNA but I believe the same also applies for human DNA.For these reasons, amplification of the integrated viral genome by PCR has been the preferred method for the diagnosis of HIV infection in children for many years (11). However, this method requires venipuncture in newborns for blood sampling and preparation of lymphocyte pellets, both of which are difficult to perform, particularly in developing country settings.
Dried blood spot (DBS) samples are an interesting alternative for lymphocyte pellets since only a few droplets of blood are required and can be directly collected on a filter paper. Storage and shipment of filter papers is easy since they can be kept at room temperature and DNA has a good stability in dried samples. Finally, DBS have been used for the detection of HIV-1 genome by PCR since 1991 (3-5) with good sensitivity and specificity.
Bacteria need water to grow and reproduce so it probably won't decompose into bacterial waste as long as the sample is completely dry. But DNA, while more stable than RNA, does still decompose over time so just out of interest, I looked into how long it takes for a strand of DNA to degrade and found this article:It is suppost to last for decades, not years. I can do a DIY paper but I'm not sure if the blood in the paper will decompose into bacteria waste after decades.
Since this DNA was collected from fossils that were probably in contact with groundwater at various points during fossilization and subjected to conditions that aren't exactly conducive for preservation, a DNA sample that is kept completely dry in ideal conditions should last much longer than this. Possibly even indefinitely since it is the reactions with water that are thought to be responsible for most bond degradation in the long run.By comparing the specimens' ages and degrees of DNA degradation, the researchers calculated that DNA has a half-life of 521 years. That means that after 521 years, half of the bonds between nucleotides in the backbone of a sample would have broken; after another 521 years half of the remaining bonds would have gone; and so on.
The team predicts that even in a bone at an ideal preservation temperature of −5 ºC, effectively every bond would be destroyed after a maximum of 6.8 million years. The DNA would cease to be readable much earlier — perhaps after roughly 1.5 million years, when the remaining strands would be too short to give meaningful information.
Storage at –20°C to –80°C may well provide adequate conditions depending on the quality and quantity of DNA desired and the time frame in which the sample will be stored. However, neither of these conditions will maintain DNA quality equivalent to maintenance at liquid nitrogen temperatures over extended time periods (e.g. decades).
In contrast to storage of DNA in solution at very low temperatures, it is also possible to store DNA dried. This can be a practical alternative for long-term storage. In addition to reducing molecular mobility, dehydration also removes water that can participate in hydrolytic reactions. There are several methods of removing water from liquid preparations; these include spray drying, spray freeze drying, air drying or lyophilisation.
So basically you have two options if you want to store a DNA sample for decades. You could store it in liquid nitrogen or store it dried. Both techniques will keep the DNA relatively intact for decades. If you do decide to take the dried route, you could also slow down the rate of degradation even further and therefore maximize your chances of retrieving the DNA mostly intact by keeping the sample away from heat, sunlight, humidity, oxygen, etc.To ensure high quality microarray results, we recommend the following DNA storage strategies:
- Short-term storage (weeks) at 4°C in Tris-EDTA
- Medium-term storage (months) at –80°C in Tris-EDTA
- Long-term storage (years) at as –80°C as a precipitate under ethanol
- Long-terms storage (decades) at –164°C or dried
Here's another article of interest:
So basically you have two options if you want to store a DNA sample for decades. You could store it in liquid nitrogen or store it dried. Both techniques will keep the DNA relatively intact for decades. If you do decide to take the dried route, you could also slow down the rate of degradation even further and therefore maximize your chances of retrieving the DNA mostly intact by keeping the sample away from heat, sunlight, humidity, oxygen, etc.
Are you sure you need to map the whole genome? Rather than trying to sequence everything, it would make far more sense, economically speaking, to only look at specific parts of the genome (e.g. known SNPs or VNTRs) if your goal is to use the DNA to identify individuals and/or gain information about their health.Legal purposes.