Fig. 1. The C3G locus and the mutated allele C3G^gt. (A) The 124 kb C3G locus comprises 24 exons. The start of translation is encoded by exon 1. The gene trap insertion occurred in intron 1. Intronic probe 1 is used for Southern analysis of genomic DNA (probe 1). The major product of the native locus is a 1095 aa protein with a carboxy-terminal CDC25-like catalytic domain (black box) and 4 internal Crk-SH3 domain-binding sites (black stripes) and one p130^cas-SH3 binding site (grey box). Probe 2 used for northern analysis and in situ hybridisation of paraffin sections of embryos is indicated (probe 2). The gene trap disrupts the coding region after the first 19 codons (black arrowhead). The mutated allele, C3G^gt, codes for a fusion between the first 19 aa of C3G, ß-galactosidase (ß-gal) and neomycin phosphotransferase (neoR). (B) Southern analysis of genomic DNA isolated from embryos of heterozygous intercrosses hybridised with probe 1 as indicated in A. Bands of 12 kb and 16 kb for the wild-type and the C3G^gt mutant allele, respectively. Homozygous mutant, mt; heterozygous, ht; wild type, wt.