Evidence for the presence of hairpin chloroplast DNA molecules in barley cultivars

Summary Total DNA was extracted from young green and etiolated barley leaf shoots and run on 2D neutral/alkaline agarose gels. This technique showed the presence of molecules which behaved as though their single-stranded length was twice their double-stranded length. This behaviour was sensitive to S1 nuclease. Our conclusion is that these DNAs are hairpin molecules. They are homologous to sequences found throughout the barley chloroplast genome. This type of molecule is present in uncut DNA with a continuous range of sizes varying between 0.5 and 15 kbp in our experimental conditions. The origin and possible biological function of these molecules is discussed.