Fanconi anaemia is a rare autosommal recessive disorder characterized by congenital abnormalities, progressive bone marrow failure, and cancer susceptibility. The hypersensitivity to agents that produce DNA cross linking is the basis for a diagnostic test. DNA damage by DNA cross linking agents such as MMC activates the FA protein complex leading to activate the monoubiquitination of FANCD2, resulting in its targeting to nuclear foci that also contain BRCA1 and BRCA2/FANCD1, proteins involved in DNA repair.Damage caused by ionizing radiation activates ATM which phosphorylates FANCD2 in addition to several other proteins to coordinate the S phase checkpoint response.There is interaction pathways between the FA proteins and other proteins involved in DNA damage repair, such as ATM, BRCA1 and BRCA2.