Fig. 1. Iro proteins and genomic organization of the Iro genes. All Iro proteins conform to the same structure with two strongly conserved domains: a homeodomain of the TALE class (HD) and the Iro box (ib), a motif reminiscent of the central part of the EGF repeats of the Notch receptor protein. Generally, Iro genes are chromosomally arranged in groups of three genes. Vertebrates paralogous genes are labelled with similar colours. A detailed physical map of the D. melanogaster (Dm) Iro-C is shown at the bottom of the figure. Molecular lesions associated with iro¹ (chromosomal breakpoint), iro^rF209 (P element insertion), and iro^DFM3 and mirr^e48 (chromosomal deletions) are indicated. Transcription units of the three Iro Drosophila genes are shown in red. Coordinates are in kb. (Data taken from Bosse et al., 2000; Gómez-Skarmeta et al., 1996; McNeill et al., 1997; Netter et al., 1998; Peters et al., 2000.)