The yield and quality of DNA extracted from blood samples stored under various conditions

: The effect of different conditions of blood sample storage on the yield and quality of the extracted DNA was studied. Samples of whole umbilical blood were divided into eight groups containing 10 samples each and stored as follows: A--no storage, DNA extracted immediately; B--24 hours at 4 degrees C; C--24 hours at room temperature; D--7 days at 4 degrees C; E--3 months at -18 degrees C; F--6 months at -70 degrees C; G--14 days at -70 degrees C, the samples were thawed one time and frozen again; H--14 days at -70 degrees C, the samples were 3 times thawed and frozen. DNA was isolated and yields quantified by spectrophotometry at 260 and 280 nm. The average DNA yield in the individual groups ranged from 574.5 to 1,075 micrograms per 10 ml of whole blood. Although variations in the yield of DNA were observed both within and among groups, there were no significant changes with respect to different storage conditions. However group H yielded significantly more DNA (900 micrograms/10 ml, p less than 0.05) compared to the control group A. After digestion with restriction endonuclease and electrophoresis in agarose gel, all DNA preparations were found to be of high molecular weight and in digestible condition. The results can be used to advantage in storing DNA for purposes of molecular diagnosis of genetic diseases.