DNA stability/degradation over time - (Mar/27/2006 )
I have a question regarding DNA stability- Does anyone know how long genomic DNA from a tissue sample can last without degrading prior to putting it in lysis buffer? Meaning, if the sample is garnered, how long can one wait before placing it in lysis buffer without suffering any DNA degradation due to nucleases?
hi ! DNA is a very stable molecule and it can be stored for prolonged times provided there are no nuclease contamination. nuclease contamination comes due to microbial contamination so storage under sterile conditions is a necessity. can store at -20/ -80 C for months. however repeated freeze thawing might affect its stability. aliquoting can overcome this problem. rough handling may shear the DNA.
Thanks for your timely response! I was just wondering, if you know when nucleases become a problem? I know you said that nucleases are due to microbial contamination, but there are nucleases inside the cell as well. Are these problematic as well when cells are lysed?
If you keep your sample frozen there shouldn't be much of a problem.
In purifying DNA you "wash" away protein (commercial kits) or you separate them (phenol::chloroform), and in some instances you will also use proteinase K to make sure your proteins are destroyed. (you'll never reach 100% destruction as it's still a biochemical process but after prot. K you will wash/separate more).
I've a DNA sample extracted from tissue stored at 4°C since 99 and it work very well!!!!
i agree with vairus ! there should not be any problem when you are storing at low temperatures