At the cellular level, Recq5 knockout (KO) mouse embryonic stem cells display an increase in sister chromatid exchanges (SCEs) due to an elevated frequency of homologous recombination (HR) in repairing DNA double-stranded breaks (DSBs) [30], resembling Dr. German’s initial observation in cells derived from Bloom’s syndrome patients [7]. This evidence concerns the gene RECQL5 and Bloom syndrome.