The gene-trap (containing a betageo reporter-selection gene cassette) inserted 13,940 bases from the start intron 3. This leads to the putative generation of a truncated fusion protein with betageo containing the first 218 amino acids (including part of the fork-head box domain) of the target gene and the loss of C-terminal 239 amino acids (containing part of the fork-head box domain and the SIN3 binding domain). Homozygous mutants expressed low levels of the native gene indicating the generation of a hypomorphic allele.