Due to an error in the production process, Table 1 contained two errors. In the second row of the table, Brca1+/+ was incorrectly labeled as Brca1ΔC/ΔC, and Brca1+/ΔC was incorrectly labeled as Brca1+/+. These errors have been corrected, and the revised version of Table 1 now appears with the paper online.
The production team apologizes for this error.