Extended Data Figure 4. Primase defect leads to defective long leading strand synthesis.

a, CHEF electrophoresis analysis of DSB repair in PRI2 (wt) and temperature-sensitive pri2–1 mutant followed by Southern blot analysis using ADE1-specific probe (one representative experiment from n=3 independent biological repeats). BIR: BIR repair product; HC: half-crossover resulting from fusion between fragments of recipient and donor Chromosome III (see Extended Data Fig. 9a for details); ChrI: Chromosome I; Uncut: full-length recipient chromosome. b, Top: Schematic of experiment to characterize BIR progression following depletion of Pol1 (pol1-degron) by addition of IAA. Bottom left: Degradation of AID-tagged Pol1 verified by Western Blot. Bottom right: AMBER analysis of BIR synthesis. The means ± SD (n=3 independent biological repeats) indicated by error bars. c, Proposed model explaining the role of primase and Okazaki fragment synthesis in stabilization of leading strand.