Microsatellite genotyping. a) Localisation of the intragenic polymorphisms on the physical map of the murine Cftr gene. b) Analysis of the four informative intragenic microsatellites by direct blotting electrophoresis. c) Microsatellite alleles were ascertained by arbitary repeat units. The alleles for all four microsatellites which are representative of the two CF inbred lines (CF/1 and CF/3)and hence directly linked with the disease causing allele carrying the insertional vector pIV3.5H in Cftr exon 10 have been given the number 20.