Chromosomal DNA extraction after restriction endonuclease treatments: a study by microdensitometry and electrophoresis.

The appearance of G- and C-banding patterns on metaphase chromosomes from the Don cell line (Cricetulus griseus) was accompanied by extraction of chromosomal DNA. A microdensitometric technique was employed to measure the loss of DNA produced by Hin dIII, Hae III and Eco RI endonuclease digestion on fixed chromosomes, from 0.5 to 24 h of treatment. Agarose gel electrophoresis was carried out to estimate the size of the DNA fragments extracted after digestion by Alu I and the restriction endonucleases already mentioned. Results obtained show that Alu I and Hae III, which possess 4 base pair recognition sequences, caused higher DNA extraction than enzymes with recognition targets of 6 base pairs (Hin dIII and Eco RI). Incubation buffers induced G-banding patterns which were accompanied by DNA extraction, although this loss was lower than that produced by endonuclease treatments.