Freezing damage DNA?

Zhonglin Chai zchai at COBRA.PATH.MONASH.EDU.AU
Fri Aug 25 03:15:53 EST 1995


> In article <416ffu$8ub at enterprise.sct.gu.edu.au>
> "h.woo" <h.woo at sct.gu.edu.au> writes:
>
>| It seems that freezing and thawing repeatedly does affect DNA, as far as
>| using genomic DNA as PCR template is concerned. I keep my genomic DNA
>| stock solutions at 4C.
>
>I've heard the reasons why multiple freeze-thaw cycles of PCR primer stocks
>could limit the PCR, but I haven't heard anything about genomic DNA samples.
>How could this happen? Are the samples already restriction digested or just
>stored as genomic DNA isolates?

Multiple cycles of freeze-thaw of both PCR and sequencing primers in my
hands never affected results. For long DNA molecules, like genomic DNA and
lambda phage DNA (40 plus kd), I always keep them at 4 degrees C.,
considering that the -20 degree C. freezing and thawing cycles would create
ice crystals, that shear or break long DNA molecules (fibres) very easily.




ZhongLin Chai

____________________________________________
Department of Pathology and Immunology
Monash Medical School
Alfred Hospital
Commercial Rd, Prahran, Victoria, AUSTRALIA
Telephone: (61 3) 276 2698
           (61 3) 388 1205 (home)
Fax:       (61 3) 529 6484
email:     zchai at cobra.path.monash.edu.au
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