The past few years have witnessed a considerable expansion in our understan
ding of the pathways that maintain chromosome stability in dividing cells t
hrough the identification of genes that are mutated in certain human chromo
some instability disorders. Cells that are derived from patients with Fanco
ni anaemia (FA) show spontaneous chromosomal instability and mutagen hypers
ensitivity, but FA poses a unique challenge as the nature of the DNA damage
-response pathway thought to be affected by the disease has long been a mys
tery. However, the recent cloning of most of the FA-associated genes, and t
he characterization of their protein products, has provided tantalizing clu
es as to the molecular basis of this disease.