Effects of DNA damage and of replisome defect on half-crossover formation.

<p>(A) Effect of mutations impairing DNA polymerases on HC formation. Results of 3 to 14 experiments performed for each strain were used to calculate the average ± SD percent of colonies containing a HC. Asterisks indicate statistically significant increases compared to the Pol⁺ (wild type) strain. See the text for P-values. For the number of colonies analyzed, see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004119#s4" target="_blank">Materials and Methods</a>. The frequency of HCs in <i>pol32</i>Δ was presented previously <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004119#pgen.1004119-Deem1" target="_blank">[12]</a>. Because no HC outcomes were observed in <i>pol1-1</i> strains among 454 analyzed colonies, we estimated that the frequency of colonies with HCs was less than 0.3%. (B) Effect of DNA damaging agents MMS (2.4 and 6 mM) and 4-NQO (5.3 µM) on HC formation. Results of 3 to 8 experiments performed for each strain were used to calculate the average ± SD percent of colonies containing a HC. Experiments performed in the absence of galactose represent no-DSB controls. Asterisks indicate statistically significant increases compared to the no-damage control.