R-loop Formation During DNA Transcription (image) University of Washington Health Sciences/UW Medicine Share Print E-Mail Caption A schematic showing how R-loops, a hybrid of RNA and DNA, can form during DNA transcription when the messenger RNA chain being assembled by the RNA polymerase binds to one of the DNA strands. R-loops effectively block replication. Credit Merrikh lab/UW Medicine Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.