[Effect of low temperatures on molecular parameters of DNA]

Cryoconservation effects on macromolecular parameters of DNA from reproductive cells of fishes are studied as well as cryodamages of DNA in solutions under various freezing conditions, by the viscometry method. A dependence of the low temperature action on DNA concentration in solution and on the action duration is determined. It is stated as well that the nitrogen temperature action on the biopolymer solution results in the formation of both double- and single-stranded breaks. The cryoprotector (ethylenglycol 12%) added into the solution frozen prevents from the formation of double-stranded breaks and decreases the number of single-stranded ones. The long-term (0.5 year) keeping of the biopolymer solution at -196 degrees C both under the cryoprotector (20% 1.2-propanediol) protection and without the cryoprotector induces the significant number of single-stranded breaks. Mechanisms of cryodamages of DNA macromolecules in cells and under the nitrogen temperature action are discussed.