Considering the chromosomal breakage phenotype of hSNM1B/Apollo-depleted cells and the nuclease's role in DNA replication, repair and telomeric maintenance, it seems reasonable to consider whether a null mutation could cause a chromosome instability syndrome in humans similar to Fanconi anemia, Nijmegen breakage syndrome or ataxia telangiectasia. This evidence concerns the gene DCLRE1B and ataxia telangiectasia.