This allele occurred in descendants of a gamma irradiation experiment. The underlying mutation was identified as a 67 bp intragenic deletion. The deletion causes a frame shift resulting in a truncated 376 amino acid protein but does not affect the first 228 residues, including the characteristic WH DNA-binding domain. The mutant protein is predicted to bind to its DNA targets but fails at transcriptional activation or repression because the specific C-terminal domains are missing.