"A technologist in a tissue bank who performed HLA typing by DNA analysis was asked to bank all DNA extracted from specimens rec
eived in the laboratory so as to maintain the highest quality of nucleic acid for the longest period. How should the DNA be stored to satisfy this request?
The DNA could be dried -through the process of lyophilization- or stored, as a precipitate of ethanol, in liquid nitrogen (temperatures below -80 degrees Celsius). The aim is to reduce water in the stored samples as much as possible because the water can be involved in natural hydrolytic reactions (depurination, depyrimidination, deamination, and hydrolytic cleavage) that could degrade the nucleic acids of the DNA.
If the DNA is stored while being used regularly it is not advisable to store it as a precipitate of ethanol. It should be stored in aqueous form but in a slightly alkaline pH of about 8.5 to prevent acid-catalysed degradation processes.
