A technique for visualizing under the electron microscope the complementary regions shared by a specific eukaryotic RNA and a segment of one strand of a DNA duplex. The RNA-DNA hybrid segment displaces one of the DNA strands, causing it to form a loop; hence the name of the technique. Double-stranded regions appear thicker than single-stranded regions in electron micrographs. Introns cannot hybridize with mature mRNA (from which introns have been removed); thus, one intron results in two R loops, two introns yield three R loops, etc.
See Chronology, 1977, Chow and Berget.
Subjects: Genetics and Genomics.