Micro extraction of DNA from whole blood and amniocytes

We describe methods for extracting genomic DNA from a small amount of whole blood or cultured amniocytes. Nuclear DNA was extracted from whole blood spotted on blotting paper. Relatively large molecules of DNA with the average amount of 7-9 micrograms was extracted from 1 ml of blood spotted and stored for at most two years, being roughly 1/3 of that extracted directly from fresh whole blood. The estimated minimum amount of whole blood that gives a suitable autoradiogram of Southern hybridization was 0.3 ml. Another series of amounts of whole blood or an amniocyte suspension were molded in low-melting agarose into an 100 microliter gel block. The DNA extracted from a block that was made from at least 0.25 ml of whole blood, or from 1.25 x 10(5) amniocytes (equivalent to 1/8 of the number of confluent cells in a 25 cm2 culture flask) resulted in one suitable Southern analysis. Both methods described here are applicable to the diagnosis of newborns and/or fetuses at risk of a genetic disease and to the diagnosis of a patient from whom a large amount of blood material is difficult to obtain. These methods also make a long-way transportation of the materials possible.