Effects of methyl iodide fumigation on biological specimen DNA

Abstract

Effects of fumigation with methyl iodide or methyl bromide/ethylene oxide mixed gas against biological specimen DNA were examined using dried samples of spinach leaf, muscle and bone marrow of chicken, mushroom and yeast. The condition of fumigated DNA varied, depending on species, tissue, extraction method, and fumigant. Fumigation caused a decrease in the yield of high molecular weight DNA, and sometimes smears of degraded DNA were observed on electrophoresis gels. However, PCR amplification and direct sequencing of fumigated DNA was hardly affected: there was no difference in the DNA sequence of all PCR products. Methyl iodide had less effect on DNA when compared with methyl bromide/ethylene oxide mixed gas. Fumigation caused protein denaturation and changed protein solubility. In addition, DNA degradation increased when extracted by kits without chloroform treatment. We conclude that the decrease of high molecular weight DNA yield is caused mainly by denatured proteins obstructing DNA extraction, rather than direct degradation of DNA during fumigation.