Analysis of 5′ end-directed RNase H cleavages in RNAs Md1 through Md10 using M-MuLV reverse transcriptase. The hybrid substrate shown schematically at the top of each panel contained the indicated 5′ end-labeled (A) or 3′ end-labeled (B) RNA. Substrates were treated with M-MuLV reverse transcriptase and analyzed as described in Fig. 2. In Md1, the cleavage sites are found between the following nucleotides from the RNA 5′ end: site D is +8/+9, site E is +13/+14, site F is +16/+17, site G is +19/+20, site H is +22/+23, and site I is +27/+28.