FIG. 2.

A discrete class of RNAs is essential for human chromosomal DNA replication. (A) Size fractionation of RNA prepared from ArE by gel filtration. Individual fractions were analyzed by agarose gel electrophoresis, and a 100-bp DNA ladder was used as a molecular weight marker (lane M). (B) Functional testing of the size-fractionated RNA. n, number of experiments. Template nuclei were incubated with the RNA purified from a constant volume of the indicated gel filtration fractions, supplemented with fractions QA and ArFT. Proportions of replicating nuclei were determined as described in the legend to Fig. 1.