Herring Sperm DNA
Resuspend 1 g of herring sperm in a convenient volume (50 ml of H2O) by sonicating briefly. The DNA is now ready to be sheared into short molecules by sonication. Place tube containing herring sperm DNA solution in an ice bath (the tube must be stable even if ice begins to melt). Place the sonicator probe in the DNA solution (without touching bottom of the vessel). Turn on the sonicator to 50% power for 10 minutes, or until there is a uniform and obvious decrease in viscosity. Do not allow the tube containing the DNA to become hot to the touch. After sonication, dilute the DNA with H2O to a final concentration of 2 mg/ml, freeze in 50-ml aliquots, and thaw as needed.
Note:
Some investigators recommend that salmon sperm DNA be boiled and chilled before each use. In general, this solution is not sterilized.
