Why ultra low freezer - (Jun/27/2006 )

Hi everyone,

This might be a rookie question but I have had this question for awhile. I have noticed that most labs use ultra-low freezer for DNA or sample storage (-70C or lower). Why is -20C not enough for storage? Isn't freezing samples at -20C enough to stop any reaction because there's no free moving water? Thanks.

hi
at -20°, biological processes still occurs. -70° is supposed to be the limit at which the thermal agitation is not enough important to allow any biological process.