Blue lines, DNA strands; orange lines, RNA strands; arrowheads, direction of strand extension; smaller navy font, DNA metabolism processes; bigger black font, various R-lesions. A. Two types of R-loops in relation to replication. B. The model of chromosomal fragmentation in the absence of RNase H activities. Mis-maturation — incomplete maturation of Okazaki fragments. The last step with pink arrow — any cellular ssRNA endoribonuclease.