Figure 1.

Representative pedigree of 239B transmission. The phenotypes depicted represent the percentages obtained for the total mice analysed for each of the five matings (A–E) adapted to a litter size of 10 pups. Genotyping was performed by Southern transfer and hybridisation using genomic mouse DNA probed with the lacZ gene and phenotypic analysis was determined by X-Gal staining of erythrocytes. All crosses were performed using P.O. heterozygote transgenic mice and P.O. wild-type mice of the opposite sex. Following convention, circles represent females and males are depicted by squares. It can be seen that the phenotype of the offspring depends not only on the phenotype of the transgenic parent but also grandparental effects are evident with male transmission. When the grandmother (female parent cross C) has a silenced transgene the silencing modification is not always reversed through the subsequent male germline (male parent cross E), resulting in some progeny with no transgene expression.