sentences:  During mitosis in "Drosophila" DNA damages caused by exogenous agents are repaired by a homologous recombination process that depends on mei-41(ATR).Mutants defective in mei-41(ATR) have increased sensitivity to killing by exposure to the DNA damaging agents UV , and methyl methanesulfonate.Deficiency of mei-41(ATR) also causes reduced spontaneous allelic recombination (crossing over) during meiosis suggesting that wild-type mei-41(ATR) is employed in recombinational repair of spontaneous DNA damages during meiosis.