Fanconi anemia (FA) is a hereditary chromosomal instability syndrome with cancer 
predisposition. Bone marrow failure resulting in pancytopenia is the main cause 
of death of FA patients. Diagnosis of FA is based on their cellular 
hypersensitivity to DNA crosslinking agents and chromosome breakages. Somatic 
complementation experiments suggest the involvement of at least eight genes in 
FA. The gene for complementation group A (FANCA) is defective in the majority of 
FA patients. We show here that mice deficient of FANCA: are viable and have no 
detectable developmental abnormalities. The hematological parameters showed a 
slightly decreased platelet count and a slightly increased erythrocyte mean cell 
volume in mice at young age, but this did not progress to anemia. Consistent 
with the clinical phenotype of FA patients, both male and female mice showed 
hypogonadism and impaired fertility. Furthermore, embryonic fibroblasts of the 
knock-out mice exhibited spontaneous chromosomal instability and were 
hyper-responsive to the clastogenic effect of the crosslinker mitomycin C.