sentences:  This predisposition to cancer may be linked to the DSBs occurring at the development of lymphoid cells.Two adult siblings, both heterozygous for two particular NBS1 nonsense mutations displayed cellular sensitivity to radiation, chromosome instability and fertility defects, but not the developmental defects that are typically found in other NBS patients.These individuals appear to be primarily defective in homologous recombination, a process that accurately repairs double-strand breaks, both in somatic cells and during meiosis.