An improved method for DNA extraction from paraffin sections

The acquisition of comparable quality and quantity of DNA extracts is the p rerequisite to the success of comparative genetic analyses. Although severa l DNA extracting protocols on paraffin sections have been introduced, the i mportance of deparaffinization, the procedure for obtaining an adequate hem atoxylin staining, the significance of the ratio of the cell number to the enzyme volume, and a practical means for monitoring the digestion process h ave not been sufficiently addressed. These, however, are the most important factors accountable for a failure of DNA extraction. To minimize the impac t of these factors, we have developed several unique strategies, including: (1) incubating sections at 80 degreesC for 30-60 minutes prior to xylene t reatment, (2) checking each section to insure the complete removal of paraf fin; (3) treating hematoxylin stained sections or cells with de-staining so lutions; (4) using a micrometer inserted into the eyepiece of a microscope to estimate the number of cells collected and adjusting the enzyme volume a ccording to the cell number; and (5) monitoring the digestion process with a magnifier. With these strategies, we have been able to consistently obtai n comparable quality and quantity of DNA extracts which yielded uniform PCR products regardless of variations in tissue embedding and processing.