Fig. 3. Positional cloning of dsc-1. (A) Mutations, deficiencies and cosmids used for the positional cloning of dsc-1. (B) Genomic structure of dsc-1 and the lesions of the two dsc-1 alleles. The dark gray box indicates the homeobox, and the light gray box indicates the 3' UTR. (C) Comparison between the homeodomain of DSC-1 with the consensus Q₅₀ Paired-like homeodomain (Prd HD) (see Galliot et al., 1999), and the homeodomains of the six other Q50 Paired-like homeodomain proteins in C. elegans. The residues shaded in gray indicate the six residues that are diagnostic of the Paired class; the residues in bold indicate invariant or highly conserved residues that are not specific to the Paired class; the box indicates the Q₅₀. The qm133 mutation results in an R-to-H substitution in an absolutely conserved residue at position 53 of the homeodomain (indicated by an asterisk).