Inbreeding abolishes the effect of parental origin of a mutant Rb-1 allele on pituitary tumorigenesis in mice.

The previously reported earlier onset of pituitary tumours in cross-bred mice inheriting a mutant Rb-1 allele paternally has been ascribed to imprinting of an Rb-1-linked gene. Here, we demonstrate that, as predicted from this mechanism, there is no effect of the parent of origin of the mutation in inbred mice.