Fig. 3. Structure and expression of mutant Ecd forms. (A) Schematic representation of mutant versions of the Ecd protein in the four studied ecd alleles. Numbers are amino acid positions; asterisks denote stop codons. A 4-bp deletion in the -ray induced mutant ecd^g24 changes the reading frame, resulting in the indicated amino acid substitutions and a stop codon. (B) Western blot of the wild-type and mutant Ecd forms. A low amount of maternal Ecd is still visible in the first instar, but not in the second instar homozygous ecd² larvae. The truncated Ecd version is detected by the anti-Ecd antibody in second instar ecd^l(3)23 larvae.